GIFT   OF 
Mrs*   Burton  F«  Dinsmore 


• 

BEET-SUGAR  MANUFACTURE 


BY 

H.    CLAASSEN,    PH.D. 


AUTHORIZED  TRANSLATION  FROM  THE 
THIRD    GERMAN  EDITION 

BY 

WILLIAM  T.    HALL,    S.B. 

Instructor  in  Analytical  Chemistry 
AND 

GEORGE  WILLIAM  KOLFE,    A.M. 

Instructor  in  Sugar  Analysis 
MASSACHUSETTS  INSTITUTE  OF  TECHNOLOGY 


SECOXD    EDITION 
FIRST  THOUSAND 


NEW  YORK 

JOHN  WILEY  &   SONS 

LONDON:  CHAPMAN  &  HALL,  LIMITED 

1910 


Copyright.  1906,  1910, 

BY 

WILLIAM  T.  HALL 

AND 

GEORGE  WILLIAM  ROLFE 


THE  SCIENTIFIC   PRESS 
KOBCHT    OK  UM  MO  NO   AND 
BKOOKLVN,    N. 


TP 


PREFACE. 


THE  aim  of  this  book  is  to  refresh  the  memory  of  technical 
sugar  men  on  the  more  important  things  observed  in  the  con- 
duct of  a  sugar-factory;  it  may  serve,  furthermore,  as  a  guide 
for  beginners  in  practical  sugar-work,  and  as  a  basis  for  further 
studies. 

It  is  in  no  way  intended  that  the  book  will  replace  any  of 
the  text-books  or  handbooks  that  treat  of  the  manufacture  of 
beet-sugar;  in  fact  it  is  assumed  that  the  reader  already  has  a 
general  knowledge  of  sugar-chemistry  and  sugar-technique.  In 
such  books,  however,  that  which  is  of  utmost  importance  to  the 
practical  sugar  man,  namely,  the  theoretical  principles  upon  which 
the  methods  of  working  depend  and  the  many  rules,  tricks,  and 
numerous  other  little  things  learned  by  experience  which  are  so  neces- 
sary for  the  proper  conduct  of  a  sugar-factory,  is  either  incompletely 
treated  or  vaguely  distributed  throughout  the  other  subject-matter. 
Most  practical  sugar  men,  therefore,  will  find  but  little  that  is 
new  in  these  pages,  but  it  cannot  be  distasteful  to  them  to  have 
the  matter  briefly  summarized  so  that  they  can  look  it  over  during 
the  long  pause  between  two  campaigns. 

A  book  concerning  the  sugar-industry  can  be  written  only  by 
one  who  has  himself  had  practical  experience.  Consequently  the 
author  will  be  pardoned  and  not  considered  narrow-minded  for 
having  stated  in  many  cases  merely  his  own  experience;  at  all 
events  he  has  tried  to  make  his  treatment  of  the  subject  as  objec- 
tive as  possible  and  with  reference  to  the  experience  of  others 
in  so  far  as  he  has  learned  it  from  personal  contact  and  from  the 
literature.  Most  of  the  original  articles  which  have  been 

ill 


IV.510940 


iv  PREFACE. 

are  referred  to  in  the  back  of  the  book,  so  that  the  reader  himself 
can  look  further  into  questions  which  he  finds  are  not  treated  fully 
enough,  and  also  form  an  independent  judgment. 

H.  CLAASSEN,  Ph.D. 

DORMAGEN,    April,    1901. 


NOTE  TO  THE  SECOND  EDITION. 

THE  book  has  been  improved  by  additions  and  changes  with- 
out affecting  the  brevity  and  comprehensiveness  of  the  treatment, 

DR.  H.  CLAASSEN. 
DORMAGEN,  November,  1903. 


NOTE   TO  THE    THIRD   EDITION. 

As  in  the  second  edition,  the  author  has  made  additions  and 
changes  without  altering  the  general  plan  of  the  work.  The 
sections  on  Juice  Extraction,  Drying  the  Spent  Chips,  and  Crys- 
tallization, as  well  as  the  calculation  on  the  Steam  Consumption 
in  the  Appendix,  have  been  worked  over,  and  in  all  other  chapters 
of  the  book  the  text  has  been  revised  and  made  clearer. 

Dr.  H.  CLAASSEN. 
DORMAGEN,  January,  1908. 


TRANSLATORS'   PREFACE. 


Claassen's  "Zuckerfabrikation"  is  already  familiar  to  most 
well-informed  sugar  men.  It  has  taken  high  rank  in  the  literature 
for  its  concise  and  intelligent  presentation  of  the  vital  points  of 
process  detail  and  as  a  guide  for  manufacturers  of  some  experience. 
Much  that  has  been  treated  by  Claassen  can  be  applied  to  the 
cane-sugar  industry  as  well,  so  that  cane-sugar  experts  have 
learned  already  to  value  the  work  as  one  of  great  usefulness  when 
the  text  is  applied  with  proper  discrimination  as  to  fundamental 
differences  in  process. 

The  translators  offer  an  English  text  giving  data  of  factory 
practice  in  those  units  in  every-day  use  in  our  own  sugar  houses 
in  the  belief  that  such  will  be  welcome  to  many. 

W.  T.  H, 
G.  W.  R. 

September,  1906. 

T 


TABLE  OF  CONTENTS. 


Preface iii 

Introduction 1 

Suggestions  for  the  Success  of  a  Sugar  Factory.  Advantages  of 
good  Beets  rich  in  Sugar. 

CHAPTER   I. 

The  Delivery,  Receiving,  and  Storage  of  Beets 3 

TIME  FOR  OPENING  THE  CAMPAIGN.     Importance  of  a  Regulated 

Delivery.     Beet-cellars.     Mechanical  Unloading. 

DETERMINATION  OF  ADHERING  SOIL.     Sampling.     Deductions  for 

Heads  and  Injured  Beets.     Frozen  Beets. 

BEET-STORAGE.      Respiration    of    Beets.      Siloing.      Beet-cellars. 

Change   in    Weight   and   Sugar-loss.     Behavior   of   Injured   Beets. 

Sprouts.     Temperature  of  Stored  Beets.     Increase  in  Amount  of 

Organic  Non-saccharine  Matter. 

CHAPTER   II. 

Transportation  and  Washing  the  Beets 13 

HYDRAULIC  CARRIERS.  Construction,  Size,  and  Water-fall.  Dam- 
ming. Wrater-supply.  Sugar-loss.  Stone-eliminator. 

WASHING  THE  BEETS.  Arrangements  for  Lifting  the  Beets  and 
Water.  Centrifugal  Washers.  Drum  Washers.  Stone  Eliminators. 

CHAPTER   III. 

Weighing  and  Slicing  Beets 19 

Necessity  for  Weighing  the  Beets.  Automatic  Scales.  Feeding 
the  Beet-slicer. 

SLICING  THE  BEETS.  Construction  and  Size  of  the  Machines. 
Driving  the  Slicer.  ('over-piece.  Feeding-hopper.  Removal  of 
Foreign  Substances.  Knife-holders.  Requirements  of  a  Knife- 
holder. 

KNIVES.  "Dachrippen,"  "Konigsf elder,"  and  Double  Knives. 
Advantages  and  Disadvantages  of  these  Knives.  Importance  of 
having  the  Beets  Well  Washed. 

vii 


viii  TABLE   OF  CONTENTS. 

CHAPTER  IV. 

PAOEI 

Juice  Extraction 27 

CELL  Tissue  of  the  Beet.  Nature,  Size,  and  Shape  of  the  Cells. 
Behavior  of  the  Plastic  Membrane  towards  Heat.  Heating  the  Beet 
Slices  is  the  First  Requirement  for  Juice  Extraction. 

A.  Diffusion 28 

PROCESSES  in  the  Individual  Cells  and  in  the  Cell  Tissue  of  the 
Slices.  Osmotic  and  Diffusion  Processes.  Washing  Out  the 
Destroyed  Cells  and  Dissolving  the  Insoluble  Constituents. 

METHOD  OF  CARRYING  OUT  DIFFUSION.  The  Diffusers,  their 
Number,  Arrangement,  Form,  and  Capacity.  Relation  between 
Diameter  and  Height.  Influence  of  the  Feeding  upon  the  Upper 
Part  and  of  Discharging  upon  the  Lower  Part.  Emptying  with 
Water  Pressure.  Arrangements  for  Sealing  the  Top. 

DIFFUSION  BATTERY.  Means  for  Improving  the  Circulation  of  the 
Juice.  Influence  of  Pressure  and  Counterpressure  of  Gas  Bubbles, 
and  of  the  Cross-section  of  the  Piping.  Warming  the  Juice  by 
Calorizators  and  by  Steam  Injection.  Hot  Pressure  Water. 

METHOD  OF  WORKING  A  BATTERY.  General  Principles.  The 
Diffusion  Process.  Influence  of  the  Nature  of  the  Water  I 'sod. 
Extraction  of  Difficultly  Soluble  Substances.  Influence  of  the  Thick- 
ness of  Chips,  of  Mushy  Chips,  and  of  the  Temperature.  Density  of 
Diffuser  Juice.  Typical  Methods  of  Working.  How  Far  the  Extrac- 
tion should  be  Carried.  Amount  of  Juice  Withdrawal.  Determin- 
ing whether  the  Method  of  Working  is  Correct.  Changes  which  the 
Beet  Constituents  Undergo  during  Diffusion.  Action  of  Micro- 
organisms and  Ferments.  Decomposition  Products  of  Sugar.  Con- 
ditions for  the  Life  Activity  of  Micro-organisms. 

CHANGING  THE  METHOD  OF  WORKING.  Continuous  Diffusion. 
Diffusion  with  the  Juice  Running  in  the  Reverse  Direction.  Rapid 
Heating  with  Rapid  Running,  Hot  Juices. 

DISTURBANCES  caused  by  Frozen  or  Decayed  Beets,  by  Evolution 
of  Gases,  by  Bacteria,  by  Beets  having  Gone  to  Seed,  by  Stoppages 
in  Other  Parts  of  the  Factory,  by  Inattention  and  Carelessness,  and 
by  Leaky  Valves.  Advantages  of  Chemical  Control.  Starting  a- 
Battery  and  Sweetening  it  Off. 

The  Exhausted  Chips.  Construction.  Losses  in  Pulp.  Extent  of 
Pressing.  Influence  of  Temperature.  Losses  in  Nutritive  Substance. 

B.  Diffusion  Combined  with  Pressing  and  Recovery  of  the  Sweet  Waters.     63 

ADVANTAGES  in  Carrying  Back  the  Sweet  Waters.  Yield  of  Sugar 
and  Dry  Substance.  Various  Methods  of  Working. 

RETURN  OF  THE  SWEET  WATERS  to  the  Diffusers.  Prevention  of 
Bad  Pressures,  Formation  of  Foam,  and  Phenomena  of  Fermenta- 
tion. Clearing  the  Waste-water  \>y  Settling.  Return  of  tin-  Mixed 
or  Separated  Waters.  Content  of  Sugar  and  Dry  Substance  in  the 
Spent  Chips  and  Waste-waters.  Purity  of  the  Juice.  Acidity  of 


TABLE   OF  CONTENTS.  ix 

PAOB 

Waste-waters.  Treatment  of  Waste-waters  with  Lime.  Return  of 
the  Sweet  Water  from  the  Presses  to  the  Diffusers.  Filter  Presses  in 
Diffusion. 

PRESS  DIFFUSION'.     Method  of  Working.     Advantages  and  Disad- 
vantages as  Compared  with  Diffusion. 
C.  The  Scalding  Process 70 

Method  of  Working.     Amount  and  Purity  of  the  Raw  Juice.     The 
Compressibility  of  the  Sliced  Chips.     Advantages  and  Disadvantages 
of  the  Process.     The  Profitableness.     Value  and  Estimation  of  the 
.  Spent  Chips.     Changes  in  the  Process. 


CHAPTER  V. 

Drying  the  Spent  Chips 74 

Advantages  of  Drying.     Direct  Drying  by  Means   of  Furnace 

Gases  in  Ovens  or  Drums.     Control  of  the  Drying.     Dust  Catchers. 

Drying  by  Steam.     Advantages  and  Disadvantages  of  the  Latter. 

Use  of  Boiler-room  Gases  for  Drying;  or  for  Preliminary  Heating. 
Changes  in  Pulp  which  Take  Place  during  Drying.     Amount  of 

Dried  Chips  and  Losses.     Keeping  Qualities.     Preparation  of  Chips 

with  Molasses. 


CHAPTER  VI. 

Diffuser  Juice,  Its  Preliminary  Purification  and  Warming 81 

NATURE  AND  COMPOSITION  of  Raw  Diffusion-juice.  Injurious 
Non-sugars.  Mechanical  Filtration  by  Pulp-eliminators.  Albumjn 
Filters.  Chemical  Purification. 

PRELIMINARY  WARMIXG  of  the  Juice.  Open  and  Closed  Heaters. 
Changes  in  the  Juice  during  the  Heating.  Addition  of  Lime.  Clean- 
ing the  Heating-tubes. 


CHAPTER   VII. 

Defecation 87 

Solubility  of  Lime. 

MILK-OF-LIME  DEFECATION'.  Preparation  of  Milk  of  Lime. 
Advantage  of  Fresh  Milk  of  Lime.  Dry  Defecation.  Rules  for  a 
Scientific  Defecation.  Apparatus  Required.  Continuous  Defeca- 
tion. Action  of  the  Two  Methods  of  Defecation.  Advantages  and 
Disadvantages  of  Each.  Mechanical  Action  of  Lime  upon  Raw  Juice. 

CHEMICAL  Acnox  OF  LIME  UPON  NON-SUGARS,  their  Precipitation 
and  Decomposition.  Behavior  of  Alkalies  during  the  Process. 
Most  Favorable  Temperature  for  Defecation.  Cold  Defecation. 
Duration.  Amount  of  Lime  Necessary. 


x  TABLE    OF  CONTEXTS. 

CHAPTER    VIII. 

PA  HE 

Carbgnatation 97 

Carbon  Dioxide.  Carbonatation -tank.  Distributing  Devices  for 
the  (las.  Heating  the  Juice  in  the  Tanks.  Depth  of  Liquor  and 
Height  of  the  Tanks.  Foam-preventers.  Removal  of  the  Spent 
*  .uses.  Carbonic-acid-gas  Pumps. 

METHOD  OF  CARRYING  OUT  THE  PROCESS.  Changes  which  Take 
Place  in  the  Carbonatation.  The  Chemical  Reactions.  Causes  for 
the  Precipitation  of  Lime  Sucrate.  Over-saturation.  Continuous 
Carl>onatation.  Carbonatation  Troubles.  Causes  of  a  Too  Slow 
Carbonatation.  Strong  Frothing.  Sugar  Losses. 

CHAPTER  IX. 

Treatment  of  the  Sludge  or  Scums 1 10 

Scum-pumps.  Filter-presses,  Chamber-presses,  Frame-presses. 
Size  of  Presses.  Cleaning  the  Canals.  Choice  of  Cloth.  The  Fil- 
tration. Cause  of  Slow-running  Presses.  Sugar.  The  Filter-cake. 
Amount  of  Sugar  in  the  Unwashed  Cake. 

SxvEETEXixf!  OFF  THE  CAKE.  Adjusting  the  Pressure  of  the  Pump. 
T«ime  Required.  Temperature  of  the  Waters.  Separation  of  the 
Waters  according  to  the  Density.  Removal  of  the  Cake  from  the 
Presses. 

CHAPTER  X. 

Final  Carbonatation  and  Filtration 122 

Reheating.     Second  Addition  of  Lime. 

SECOND  AND  THIRD  CARBON  \T\TIO.\S  with  Carbonic  Acid  or 
Sulphurous  Acid.  Continuous  Carbonatation.  The  Proper  Alka- 
linity of  the  Thin  Juice. 

FILTRATION  by  Different  Methods. 


CHAPTER  XI. 

Other  Purifying  and  Clarifying  Agents 128 

Numl>er  and  Nature  of  Different  Agents  that  have  been  Recom- 
mended.    Use  in  the  Battery  and  Upon  the  Juices. 


CHAPTER   XII 

Evaporation 1 :{ 1 

Amount  of  Thin  Juice.  Con-t ruction  of  a  Single  Effect.  Heat 
Transference  and  Re-i-tanr.  a^.uii-t  Il«-at  Conduction.  Best  Condi- 
lions  for  Heat-transference.  Advantage  of  Simplicity.  Efficiency 


TABLE   OF  CONTENTS.  X 

PAOl 

of  a  Single-effect  Apparatus.  Juice-level  and  Juice  Circulation. 
Taking  Away  the  Condensed  Water  and  Uncondensed  Gases. 
Influence  of  the  Nature  of  the  Metal  Upon  the  Heat-transference 
and  the  Formation  of  Scale.  Removal  of  Scale.  Influence  of  the 
Viscosity  of  the  Juice,  the  Boiling  Temperature,  and  the  Fall  of  Tem- 
perature Upon  the  Transference  of  Heat.  Prevention  of  Mechanical 
Loss  of  Sugar  Due  to  Entrainment  and  Leaky  Valves. 

MULTIPLE-EFFECT  APPARATUS.  Repeated  Utilization  of  the  Heat 
and  the  Extent  to  which  this  is  Possible.  Relative  Size  of  Heating- 
surfaces.  Heat-transference  of  the  Last  Effects.  Taking  Part  of 
the  Steam  for  Heating  and  Cooking  the  Juice.  The  Juice-cooker. 
Difficulties  Connected  with  the  Working  of  Juice-cookers.  The  Heat- 
transference  Coefficients.  Use  of  Exhaust  Steam.  Amount  of  Con- 
sumption. Influence  of  the  Juice  Withdrawal.  Use  of  Superheated 
Steam  and  Steam  Injection  Apparatus. 

SUGAR  Loss  During  Evaporation.  Dependence  upon  the  Tem- 
perature and  the  Duration. 

CONTROL  of  Evaporating-apparatus.     The  Steam  Supply.     Keep-   ' 
ing   the   Concentration    of   Sirup   Uniform.     Interruptions   in    the 
Running  of  Apparatus.     Scale  Deposit.     Inadequate  Removal  of 
Condensed  Water.     Foaming.     Leakage. 


CHAPTER   XIII. 

The  Condensation  of  the  Evaporation  Vapors _ 164 

Amount  of  Vapors  to  be  Condensed.  Air-pumps.  Injection- 
condensers.  Counter  -  current  Condensers.  Amount  of  Water 
Required.  One  Common  Condenser,  or  at  Least  a  Central  Air-pump. 


CHAPTER  XIV. 

Carbonatation  and  Filtration  of  the  Concentrated  Juice  or  Sirup 170 

Alkalinity  of  the  Sirup  and  its  Effect  upon  the  Further  Treat- 
ment and  upon  the  Ash  of  the  Sugar.  Continuous  Saturation 
with  Carbonic-  or  Sulphurous-acid  Gas.  Addition  of  Lime.  Fil- 
tration. 

Carbonatation  and  Filtration  of  "Mittelsaft." 
Nature  of  the  Sirup.    Content  of  Lime  Salts. 

CHAPTER  XV. 

Sugar-Boiling 175 

Construction  and  Size  of  Vacuum-pans  and  the  Heating-surfaces. 

BOILING    IN    GRAIN.     Practical  Experience.     Actual    Processes 

Taking  Place.      Saturation.      Supersaturation.      Super-saturation- 


xii  TABLE   OF  CONTENTS. 

PACK 

coefficient.  Conditions  Required  for  the  Formation  of  Grain.  Fur- 
ther Growth  of  Crystals.  Extent  of  Supersaturation.  Uninter- 
rupted or  Intermittent  Injection  of  Juice.  The  Art  of  Sugar-boilinjr. 
Relation  between  the  Duration  of  the  Boiling  and  the  Yield. 

FINISHING  OF  THE  MASSECUITE.  Methods  for  Discharging  it  into 
the  Massecuite-tanks.  Tank  and  "  Sudmaischen "  Work.  Use  of 
Oystallizers. 

The  Control  Apparatus. 

bestruction  of  Sugar  during  Boiling.     Mechanical  Losses. 

DISTURBANCES  IN  BOIIJNG.  Heavy  Boiling.  Foaming.  Hard 
Lumps  of  Massecuite. 

Variations  in  Methods  of  Conducting  Boiling-in-grain  Process. 


CHAPTER   XVI. 

Working  up  the  Massecuite 196 

Coolers  or  an  Ordinary  Mixer. 

Work  with  Crystallizers.  Dependence  upon  Degree  of  Super- 
saturation.  Work  in  the  "  Kochmaischen."  Rate  of  Crystalliza- 
tion. Purity  of  the  Sirup. 


CHAPTER  XVII. 

The  Centrifugal  Work 202 

The  Centrifugals.  Transportation  of  Massecuite  to  the  Centrif- 
ugals. Causes  of  Difficult  Centrifugal  Work:  Fine  Crystals,  Foamy 
Massecuites,  too  Great  Cooling.  Remedies. 


CHAPTER  XVIII. 

Raw  Sugar  and  Its  Preparation 207 

Composition   and    Nature   of   Raw   Sugar.      Its   Purity,    Color, 
Alkalinity.     Nature  of  the  Crystals.     Behavior  towards  Storage. 
Transportation  of  the  Sugar  from  Centrifugals.     Shaking-sieves. 
Lumps.     Sugar  is  Allowed  to  Cool  before  Storing.     The  Storage- 
room. 

CHAPTER  XIX. 

The  Preparation  of  Sugar  Crystals ...214 

Covering  with  Water,  Steam,  or  Saturated  Sugar  Solution.  Rus- 
sian Steam-mantle.  Covering  Sirup.  Separation  of  the  Sirup 
according  to  Purity.  Treatment  of  the  Moist  Sugar  Crystals. 
Massecuite  Wash.  Yield  as  Compared  with  Centrifugal  ion. 


TABLE   OF   CONTENTS.  xiii 

CHAPTER  XX. 

PAGE 

Working  up  Centrifugal  Sugar  into  After-products 220 

Boiling-apparatus.  Different  Methods  for  Working  up  Centrif- 
ugal Sirup.  Supersaturation  Ratios  of  Impure  Sirups.  Composi- 
tion of  the  Molasses  at  Different  Temperatures  of  Completing  the 
Crystallization.  Effect  of  the  Viscosity  of  Sirups.  Conditions  for 
a  Satisfactory  Crystallization. 

(a)  WORKING  UP  SIRUP  IN  TANKS  OR  WAGONS.  Concentration  of 
the  Pure  and  Impure  Sirups.  Crystallization  Temperatures.  Tank 
Crystallization  is  Always  Unsatisfactory.  Methods  Proposed  to 
Improve  it. 

(6)  WORKING  UP  SIRUP  IN  CRYSTALLIZERS.  Concentration  of  the 
Sirups.  Cooling.  Sugar  Added  for  Grain  Formation. 

(c)  BOILING  SIRUPS  TO  GRAIN.  Keeping  the  Mother-sirup  at  the 
Proper  Degree  of  Supersaturation.  Formation  of  Grain  and  Fur- 
ther Boiling.  Completion  of  the  Crystallization  in  Crystallizers  by 
Cooling  and  the  Addition  of  a  Regulated  Amount  of  Water.  Sugar 
Losses  in  Boiling  Sirups.  Mechanical  Losses.  Decomposition 
Losses. 

After-product  Sugar.  Its  Solution.  Preparation  of  a  Better 
Sugar  by  Means  of  a  Molasses  Cover. 

CHAPTER   XXI. 

The  Purification  of  Centrifugal  Sirup 240 

Its  Saturation  with  Gas.  Filtration.  Treatment  with  Lime. 
Froth  Fermentation  of  the  Second  Massecuites.  Chemical  Puri- 
fication. Working  Back  the  Sirups. 

CHAPTER  XXII. 

Molasses  and  its  Utilization 245 

Definition  of  "Molasses."     Purity  and  Composition. 
PROCESSES  FOR  OBTAINING  SUGAR  FROM  MOLASSES.     Osmosis. 
Apparatus.     Nature  of  Osmosis  Sugar.     The  Precipitation  Pror 
Conditions  for  Satisfactory  Work.     WTorking  the  Sucrate  Back  into 
the  Regular  Process.     Advantages  and  Disadvantages  of  this  Process 
Method.     Electrolytic  Process. 

MOLASSES  AS  FODDER.     Its  Food  Value.     Mixing  with  Turf  Meal. 

CHAPTER  XXIII. 

The  Boiler-house 254 

Storage  of  Coal.     Prevention  of  Fires  in  Coal.     Condensed  Water 
for  Feeding  the  Boilers.     Injuries  to  Boilers  Produced  by  Sugar. 
Precautions  and  Remedies.     Injury  from  Oil. 
High-pressure  and  Low-pressure  Boilers. 
Precautions  to  Prevent  Rusting. 


xiv  TABLE    OF    CONTENTS. 

CHAPTER   XXIV. 

PAGE 

The  Lime-kilns 263 

TYPES  OF  KILNS.  Requirements  of  a  Good  Kiln.  Choice  of  Lime- 
stone. Burning  the  Limestone.  Dead-burning.  Temperatures  in 
the  Kiln.  Size  of  Kilns.  Charging  and  Discharging  the  Kiln. 

CARBONIC-ACID  GAS.     Purification  and  Cooling.     Amount  of  Car- 
bonic Acid  in  the  Gas. 
SULPHUROUS  ACID.     Liquid  Sulphurous  Acid.     Sulphur-burners. 


CHAPTER   XXV. 

Heat-losses  during  the  Process 272 

Heat  Balance  of  a  Sugar  Factory.  Heat-losses  in  the  Boiler- 
house.  Heat-losses  in  the  Steam  by  Cooling  and  by  Accomplishing 
External  Work.  Diminishing  these  Losses  by  Centralizing  the 
Engine-work,  by  Simplifying  the  Piping,  and  by  Superheating  the 
Steam.  Other  Heat-losses. 


CHAPTER  XXVI. 

Factory  Control  and  Determination  of  Sugar-losses 280 

Importance  of  a  Properly  Conducted  Chemical  Control.  "Super- 
intendent and  Chemists  should  Work  Hand  in  Hand.  Discovery  of 
Errors  and  Means  for  Remedying.  Difficulty  of  Making  Laboratory 
Tests  Explain  Factory  Troubles. 

DETERMINATION  OF  SUGAR-LOSSES.  Total  Loss.  Known  and 
Unknown  Losses.  Polarization  Losses.  Losses  in  Diffusion  in  the 
Scums  and  in  the  Waste  Water.  Mechanical  Losses. 


CHAPTER  XXVII. 

General  Suggestions  Concerning  the  Fitting  Up  and  Running  of  a  Beet- 
sugar  Factory 289 

Utility  Rather  than  Attractiveness.  Influence  of  Customs  and 
the  Demands  of  Commerce.  Preventing  Interruptions  in  the  Process. 
Working  the  Factory  to  its  Capacity.  Rapid  Working.  Increasing 
the  Size  of  the  Plant.  <V:uilini-.-. 

Total  Cost  of  Operating  u  Fart  my.     Campaign  Expenses. 

Practical  Control  of  the  Factory.  Kinds  of  Work.  Repairs  and 
Testing  of  Machinery,  Apparatus,  an-1  Piping. 


TABLE    OF   CONTEXTS.  xv 

CHAFFER    XXVIII. 


PACTE 


The  Utilization  and  Disposal  of  the  Waste  Products  and  Sweet  Waters 297 

Composition  and  Value  of  the  Filter-press  Cake.  Beet-earth. 
Beet-tops.  The  Waste-waters.  The  Amount  of  Waste-water  per 
100  Pounds  of  Beets.  Settling-tanks.  Chemical  Purification  of 
the  Water.  Irrigation  Fields.  Nature  of  the  Bacteria  Developed. 


CHAPTER   XXIX. 
Analysis  of  Beets,  Sirup,  and  Sugar  Products 304 

APPENDIX   T. 

Formulae,  Tables,  and  Numerical  Data 310 

Formula4  for  (1)  Calculating  Weight  of  Water  to  be  Evaporated 
from  Given  Weight  of  Thin  Juice.  (2)  Calculating  Weight  of 
Thick  Juice.  (3)  Evaporation  and  Heating.  (4)  Saturation.  (5) 
Evaporating  and  Heating.  (6)  Condensation  of  Steam.  (7)  Heat 
Transmission  through  a  Metal  Wall.  (8)  The  Fire-room. 

TABLES:  1.  Solubility  of  Lime  in  Water.  2.  Solubility  of  Lime 
in  Sugar  Solutions.  3.  Amount  of  Caustic  Lime  Contained  in  Milk 
of  Lime  at  15°  C.  (Blattner).  4.  Solubility  of  Sugar  in  Water  at 
Different  Temperatures.  5.  Temperatures  Corresponding  to  the 
Tensions  of  Saturated  Steam.  6.  Specific  Heat  of  Steam.  7.  Boil- 
ing-points of  Pure  and  Impure  Sugar  Solutions.  8.  Specific  Heats 
of  Sugar  Solutions.  9.  Sugar-losses  in  the  Evaporation  of  Alkaline 
Juices.  10.  Influence  of  Purity  on  Yield. 

VARIOUS  DATA:  Weights  of  One  Cubic  Meter  of  Different  Mate- 
rials. Specific  Weights.  Weight  of  Gases.  Specific  Heat  of  Gases 
at  Constant  Pressure.  Coefficient  of  Heat  Transmission  Data 
(Jelinek).  Sulzer's  Experiments  with  Different  Kinds  of  Tubing. 
Utilization  of  Steam  in  a  Multiple  Effect  (Claassen).  Decomposition 
of  Sugar  In  Alkaline  Solutions. 

APPENDIX  II. 

Calculations  for  an  Evaporating  Plant  and  for  the  Steam  Consumption  in 

Working  Up  100  Pounds  of  Beets 326 

APPENDIX   III. 

Comparison  of  Steam  and  Coal   Consumption   in   Different  Systems  of 

Evaporating  and  Heating 334 


BEET-SUGAR  MANUFACTURE. 


INTRODUCTION. 

THE  first  and  most  important  factor  of  success  in  beet-sugar 
manufacture  is  a  properly  cultivated  beet  rich  in  sugar.  There- 
fore the  sugar  manufacturer  should  use  all  the  means  in  his  power 
to  persuade  farmers  to  cultivate  the  beets  so  that  not  only  the 
harvest  will  prove  of  satisfactory  weight,  but  the  beet-juice  will  be 
pure  and  of  high  sugar  percentage.  The  most  certain  means  of 
accomplishing  this  is  to  purchase  the  beets  not  merely  by  weight 
but  according  to  the  amount  of  sugar  that  they  contain,  although 
this  may  not  always  be  possible.  In  the  latter  case  the  manufac- 
turer must  content  himself  with  furnishing  contracting  farmers  with 
seed  which  has  been  properly  bred  and  prescribing  the  method  of 
fertilizing  and  tillage. 

A  rich  sugar-beet  which  gives  a  pure  juice  is  not  only  absolutely 
but  proportionally  more  valuable  than  a  beet  which  gives  an 
impure  juice  or  than  a  beet  poor  in  sugar;  for  with  these  latter 
there  is  a  greater  loss  in  sugar  in  manufacture,  while  the  cost  of 
working  is  at  least  as  great  for  the  same  weight  of  beets.  Hence, 
in  comparison  with  the  sugar  yield,  the  cost  is  greater,  aside  from 
the  additional  consideration  that  the  expense  is  frequently  in- 
creased by  the  slower  process.* 

*  Further,  the  capacity  of  the  house  is  considerably  diminished  in  work- 
ing beets  of  low  purity,  owing  to  the  increased  amount  of  after-product. 
— TEANSL  ATORS  . 


2  BEET-StT.AR    MANUFACTURE. 

The  sugar-content  and  the  purity  of  beets  and  juice  not  only 
depend  upon  conditions  which  man  can  control,  but  also  upon  the 
weather,  the  climate,  and  the  nature  of  the  soil.  Where  the  climate 
permits,  the  harvesting  of  the  beets  should  be  delayed  as  long  as 
the  approaching  frost  permits;  for  the  longer  the  growth  period, 
the  more  sugar  there  will  be  in  the  beet,  the  purer  the  beet-juice, 
and  the  heavier  the  beet-yield. 

All  of  these  points,  important  as  they  are,  are  of  more  concern 
to  the  farmer  than  to  the  sugar-manufacturer.  The  activity  of  the 
latter  begins  at  the  time  the  beets  are  delivered  at  the  factory. 


CHAFFER  I. 
THE  DELIVERY,  RECEIVING,  AND  STORAGE  OF  BEETS. 

THE  time  for  opening  the  campaign  depends  not  only  upon 
the  ripeness  of  the  beets  but  also  upon  the  amount  at  the  disposal 
of  the  factory  and  upon  its  capacity.  If  a  large  quantity  of  beets 
are  to  be  worked  up  so  that  a  long  campaign  is  expected,  it  is 
advisable  to  begin  as  soon  as  possible,  say  by  the  first  or  middle  of 
September,  or  as  soon  as  the  sugar-content  of  the  beets  makes  it 
profitable.  In  order  to  have  the  necessary  data  for  deciding  this 
question  it  is  highly  desirable  to  have  a  number  of  samples  taken 
from  the  fields  and  tested  by  the  end  of  August. 

If  the  factory  expects  only  a  small  beet-harvest,  the  opening  of 
the  campaign  should  be  delayed  as  much  as  possible  so  that  from 
the  first  week  there  will  be  ripe  beets  on  hand,  and  throughout  the 
whole  campaign  only  freshly-harvested,  ripe  beets  will  be  worked 
up.  In  short,  each  year  the  work  must  be  planned  for  the  largest 
possible  average  sugar-yield;  if  the  work  is  begun  too  early,  the 
factory  suffers  by  having  beets  which  are  unripe  and  consequently 
deficient  in  sugar;  while,  on  the  other  hand,  if  begun  too  late,  the 
loss  in  sugar  will  be  considerable  on  account  of  the  prolonged 
storage  of  the  beets. 

In  southern  countries,  where  sugar-beet  culture  has  been  estab- 
lished for  some  time,  other  factors  must  be  taken  into  consid- 
eration in  beginning  and  ending  the  campaign.  There  the  beets 
ripen  very  quickly  in  summer  and  must  be  worked  up  as  quickly 
as  possible  before  the  rainy  season  of  the  autumn  causes  a  renewed 
growth  and  consequent  loss  of  sugar.  This  and  other  peculiar  con- 
ditions caused  by  the  climate  must  be  taken  into  consideration  if 

3 


4  BEET-SUGAR  MANUFACTURE. 

the  maximum  average  yield  is  to  be  obtained  from  the  beets.  On 
.  the  other  hand,  in  countries  where  continued  frost  comes  early 
the  case  is  quite  different.  In  such  places  the  campaign  must  be 
begun  early  enough  to  allow  the  farmer  sufficient  time  to  harvest 
all  of  his  beets. 

A  regulated  delivery  of  beets  is  of  great  advantage  to  the  manu- 
facturer, so  that  sometimes  contracts  with  the  farmers  prescribe 
"  how  many  beets  shall  be  delivered  each  week  and  even  how  many 
daily.  All  factories,  however,  are  not  in  a  position  to  enforce  such 
a  condition,  for  the  farmer  who  cultivates  beets  often  suffers  great 
hardships  and  disturbances  in  his  industry.  Therefore  most 
factories  require  only  a  certain  regularity  in  the  delivery  of  the 
beets,  while  others  make  no  requirements  with  regard  to  delivery, 
but  are  compelled  to  accept  the  beets  when  the  farmer  chooses  to 
deliver  them. 

Provisions  for  receiving  and  keeping  the  beets  must  be 
made  according  to  these  different  conditions.  When  the  delivery 
is  strictly  prescribed  it  is  unnecessary  to  provide  space  for  re- 
ceiving a  large  number  of  beets;  place  for  a  few  days'  supply 
is  sufficient.  When  the  delivery  cannot  be  so  systematic  the 
receiving  bins  must  have  greater  capacity.  On  the  contrary, 
where  the  beet-delivery  is  quite  unregulated  small  bins  usually 
suffice,  for  during  the  harvest  period  there  are  sure  to  be 
too  many  beets  delivered,  and  this  excess  must  be  stored  or 
siloed. 

It  is  often  injurious  to  have  too  large  a  place  for  receiving  the 
beets,  especially  when  they  are  piled  in  large  heaps  over  hydrau- 
lic carriers  fed  with  warm  water;  for  the  beets  kept  in  this  way 
for  days  or  even  weeks,  and  warmed  by  the  vapor  rising  from 
the  warm  water,  become  so  damaged  that  they  are  worked  up 
with  difficulty  and  yield  a  dark-colored  juice  of  diminished  sugar- 
content. 

The  bins,  sheds,  or  so-called  beet-cellars,  are  either  above  or 
below  ground,  and  may  have  roofs  or  be  uncovered. 

Beet-cellars   are  without  doubt  the  most   practical   places  for 


THE  DELIVERY,  RECEIVING,  AND  STORAGE  OF  BEETS.      5 

receiving  the  beets,  as  these  can  then  be  unloaded  and  placed 
in  the  hydraulic  carrier  without  the  expenditure  of  much  time 
or  labor.  It  makes  no  difference  with  regard  to  keeping  beets 
whether  the  cellar  is  covered  with  a  roof  or  not,  as  usually  they  are 
to  remain  there  but  a  short  time;  consequently  roofs  when  built 
are  merely  to  protect  the  workmen  or  draft-cattle  from  the 
weather.  When  beets  are  delivered  by  rail,  the  side  walls  of 
the  cellar  should  not  be  higher  than  the  bottoms  of  the  cars,  so 
that  the  doors  can  be  kept  open  no  matter  how  they  are  arranged, 
and  the  workmen  can  unload  without  difficulty.  In  railroad 
delivery  it  is  very  convenient  to  build  bins  with  side  walls  of 
old  wooden  sleepers  set  on  end,  the  hydraulic  carrier  being  at 
the  bottom  in  the  middle,  and  the  railroad  tracks  on  both  sides. 

The  breadth  of  the  bins  must  be  regulated  by  the  difference  in 
the  height  of  the  upper  edge  of  the  side  wall  and  the  water  level  in 
the  carrier,  so  that  the  bottom  can  be  built  sufficiently  inclined  for 
the  beets  to  slide  into  the  carrier.  If,  when  the  covering  is 
removed,  the  beets  do  not  slide  into  the  hydraulic  carrier  by 
themselves,  or  with  little  help,  considerably  more  labor  will  be 
required.  Such  constructions  are  unpractical  and  increase  factory 
expenses. 

The  cellars  should  be  located  where  the  railroad  cars  can  reach 
them  easily  and  quickly,  and  so  situated  that  turntables  can  be 
avoided,  and  the  tracks  so  arranged  that  full  cars  coming  in  will 
not  interfere  with  the  departure  of  the  empty  ones.  Beets  are 
almost  invariably  unloaded  with  forks.  The  ever-increasing  cost 
of  suitable  labor  for  this  work,  disagreeable  as  it  is  when  beets 
are  dirty,  seems  to  make  mechanical  unloading  advisable.  As  the 
present  types  of  railway  cars  have  to  be  used,  all  that  is  necessary 
are  tipping  devices  moved  by  hydraulic  power.  Many  of  these 
machines  in  present  use  in  factories  are  rather  costly  and  do  not 
meet  all  requirements.  A  good  dumping  machine  ought  to  unload 
beets  quickly  and  directly  into  the  canals  without  any  manual 
labor.  Nets  are  .also  recommended  for  discharging  beets,  large 
enough  to  take  up  the  whole  load  out  of  the  car  at  once. 

A  very  important  matter  to  be  attended  to  at  the  time  the 


6  BEET-SUGAR   MANUFACTURE. 

beets  are  delivered  is  the  determination  of  the  adhering  soil. 
Sometimes  the  amount  of  dirt  is  simply  estimated,  but  it  is  prefer- 
able to  make  a  direct  determination,  and  in  this  case  sample-taking 
is  an  important  operation.  The  best  method  is  to  take  out,  by 
means  of  the  beet-fork,  in  a  definitely  prescribed  way,  50  or  100 
pounds  of  beets  from  each  car,  and  then  determine  by  scraping, 
brushing,  or  washing  the  amount  of  adhering  soil  as  well  as  the 
weight  of  the  heads  which  are  cut  off.  As  it  is  impossible  to 
expect  to  obtain  an  absolutely  correct  average  determination  by 
taking  a  sample  for  analysis,  which  represents  only  about  J  of  one 
per  cent,  of  the  total  car-load,  it  is  nol  strange  that  such  determi- 
nations sometimes  lead  to  unpleasant  disputes  between  the  factory 
and  the  farmer.  In  order  to  avoid  these  misunderstandings  as 
much  as  possible,  it  is  well  to  have  the  sampling  carefully  checked 
by  the  seller  or  his  representative.  If  the  determination  of 
the  soil  is  made  by  washing,  a  deduction  of  one  or  two  per  cent. 
should  be  made  for  the  amount  of  moisture  adhering  to  the 
washed  beets.  The  heads  should  be  cut  off  squarely  under 
the  leaf-base  and  not  pared  off.  If  the  beets  have  large,  green 
or  empty  heads,  it  seems  but  fair  to  cut  below  the  base  of 
the  leaves,  as  such  beets  have  not  been  cultivated  with  the 
prescribed  care,  and  the  green  part  of  the  beets  as  well  as  its 
hollow  head  is  deficient  in  sugar  and  gives  an  impure  juice.  Special 
deductions  should  also  be  made,  in  all  fairness,  for  frozen,  rotten, 
or  otherwise  injured  beets,  so  far  as  their  condition  is  the  fault  of 
the  contractor. 

Injuries  which  the  beets  undergo  in  the  transportation  to  the 
factory  are  usually  borne  by  the  manufacturer.  It  is  important 
to  avoid  such  injuries  as  much  as  possible  and  to  handle  these 
injured  beets  so  that  the  injury  is  not  made  worse.  The  most- 
disagreeable  foe  to  be  contended  with  in  the  transportation  of  the 
beets  is  the  sudden  appearance  of  a  heavy  frost  which  not  only 
freezes  the  Ixjets  but  makes  it  difficult  to  unload  them,  as  they 
stick  together  in  a  hard  lump.  Frozen  beets  must  be  worked  up 
at  once,  for  they  decay  very  quickly  as  soon  as  they  heroine  thawed 
out.  Sugar-l>eets  can  stand  a  temperature  of  about  30°  F.  (-  1°  C.) 


THE  DELIVERY,  RECEIVING,  AND  STORAGE  OF  BEETS.       7 

without  freezing.  At  lower  temperatures  they  are  frost-bitten, 
but  not  thoroughly  frozen  until  the  life  of  the  plant-cells  has  been 
killed  by  the  action  of  the  frost.  Beets  which  are  still  in  the 
ground  and  covered  by  their  own  foliage  can  stand  quite  a  heavy 
frost  without  suffering,  being  at  most  but  slightly  injured  by  a  long 
period  of  frost,  provided  they  are  allowed  to  remain  in  the  ground 
until  they  have  completely  thawed  out  again. 

At  the  same  time  it  is  necessary  that  such  beets  should  be  used 
immediately  after  they  are  pulled.  Experience  has  shown  that 
rich  sugar-beets,  which  usually  have  a  firmer  tissue,  are  less  affected 
by  cold  than  beets  containing  less  sugar  and  with  softer  pulp.  When 
beets  are  transported  in  barges,  the  latter  should  be  as  shallow  as 
possible,  and  not  decked  over,  and  the  beets  should  remain  in  the 
barges  as  short  a  time  as  possible,  because  they  tend  to  become 
heated  and  are  then  harder  to  work,  yielding  a  dark  juice. 

The  Storage  of  Beets  at  the  Factory. — Beets  which  cannot  be 
used  immediately  after  their  delivery  must  be  stared  or  placed  in 
heaps  or  silos.  The  choice  of  a  proper  method  of  storage  is  im- 
portant, in  order  that  the  beets  shall  lose  the  least  sugar  and  the 
work  of  storing  and  taking  them  away  be  with  the  least  cost; 
in  short,  the  whole  arrangement  should  involve  as  little  expense 
as  possible. 

During  the  time  of  storage  there  is  bound  to  be  a  certain  amount 
of  sugar  lost  by  the  beets,  for  the  beets  respire  as  long  as  they  are 
healthy,  and  the  sugar  stored  up  in  them  is  used  up  by  this  respira- 
tion. 

The  strength  of  the  respiration  depends  upon  the  temperature 
and  the  nature  of  the  beets.  For  a  normal  respiration  access  of 
air  is  necessary.  It  would  be  erroneous,  however,  to  think  that 
respiration,  and  consequently  the  loss  of  sugar  in  beets,  could  be 
avoided  by  limiting  the  supply  of  air;  metabolism  takes  place  in 
the  beets  even  when  they  do  not  take  up  oxygen  from  the  air. 
Anaerobic  metabolism  then  occurs  by  which  the  sugar  is  con- 
verted into  alcohol  and  carbon  dioxide. 

The  sugar-content  of  beets  has  no  influence  upon  the  strength 
of  respiration,  but  it  does  affect  the  amount  of  active  protein; 


8  BEET-SUGAR  MANUFACTURE. 

the  respiration,  and  hence  the  sugar-loss  depends  accordingly  upon 
the  condition  of  the  individual  beet  and,  in  general,  is  greater  in 
unripe  beets  than  in  ripe  ones.  The  result  of  this  respiration  id 
the  conversion  of  the  sugar  into  carbon  dioxide  for  the  most  part, 
but  other  organic  substances  are  formed  to  some  extent  and  remain 
in  the  beet-juice. 

The  chief  requirement  for  keeping  beets  well  in  storage  is  that 
they  should  not  be  pulled  from  the  ground  too  early,  at  all  events 
not  before  the  middle  of  October,  and  that  they  should  be  stored 
fresh  and  uninjured  while  the  weather  is  as  cool  as  possible 
without  being  frosty. 

Beets  seem  to  keep  best  in  small  heaps  covered  with  earth; 
consequently  those  kept  for  seed  are  stored  hi  this  way.  This 
method  is  not  employed  for  storing  beets  at  the  factoiy,  because 
it  requires  altogether  too  much  space  and  is  too  expensive. 

In  countries  with  a.  mild  climate  large  heaps  which  are  uncovered 
are  to  be  preferred  to  all  other  methods  of  storage,  because  the 
amount  of  sugar  lost  is  very  small  and  the  storage  requires  but 
little  space  and  the  expenditure  of  but  little  labor.  As  beets  are 
not  injured  by  temperatures  slightly  below  32°  F.,  when  they  are 
left  undisturbed  and  are  allowed  subsequently  to  thaw  out  slowly ; 
only  those  lying  directly  on  the  outside  of  the  heaps  are  likely 
to  be  injured  by  a  short  period  of  frost,  and  these  only  when  a 
heavy  frost  and  sudden  thaw  follow  one  another  closely.  Within 
the  heaps  the  cold  penetrates  but  slowly,  even  when  quite  severe, 
and  beets  when  once  frozen  thaw  out  very  slowly,  so  that  as  a  rule 
they  are  taken  out  in  an  undamaged  condition.  Only  those  beets 
which  are  actually  killed  by  frost  are  lost  by  thawing,  for  such 
immediately  begin  to  decay.  In  countries  where  the  climate  is 
generally  mild,  loss  on  account  of  frozen  beets  Ls  so  slight  as  to  bo 
of  no  consequence  compared  with  the  good  preservation  of  the 
whole  by  the  low  and  regular  temperature  in  the  heaps. 

It  is  essential,  however,  that  the  surface  of  the  heap  should  be 
as  even  as  possible.  In  proportion  to  its  contents  there  is  less 
surface  exposed  in  a  smoothly  trimmed  heap  than  in  one  which  is 
not,  and  consequently  the  former  suffers  less  from  exposure  to  the 


THE  DELIVERY,  RECEIVING,  AND  STORAGE  OF  BEETS.      9 

weather.  Another  disadvantage  which  the  uneven  heaps  possess 
is  that  the  sharp  corners  act  as  chimneys  and  help  to  remove  heat 
and  moisture.  Consequently  the  beets  in  these  little  elevations 
are  warmer  and  moister  than  the  others  and  experience  more 
aftergrowth.  When  the  frost  comes,  the  peculiar  phenomenon 
will  be  noticed  that  the  beets  in  the  highest  portions  do  not 
freeze  first,  but  those  in  the  little  hollows  of  the  surface,  because 
here  the  cold  air  is  sucked  in. 

It  is  frequently  recommended  that  the  beet  heaps  be  covered 
over  with  a  roof.  Beets  kept  in  this  way  show  a  little  higher 
sugar-content  than  those  which  are  left  uncovered,  but  they 
decrease  more  in  weight,  so  that  the  actual  loss  in  sugar  is  not 
very  different.  In  countries  where  beets  are  taxed  upon  their 
weight  it  may  be  advisable  to  build  the  roof,  and  there  is  also  an 
advantage  to  be  gained  in  having  the  ground  thus  always  kept 
dry  and  hard,  which  facilitates  the  piling  of  the  beets  and  cartage 
back  and  forth.  In  case  there  is  no  tax  placed  upon  the  beets, 
the  cost  of  building  roofs  and  keeping  them  in  repair  will  not  be 
covered  by  the  increased  yield  of  sugar.  In  localities  where  severe 
and  early  frosts  prevail  it  is  necessary  that  the  heaps  should  be 
covered.  As  this  often  has  disadvantages  and  involves  consider- 
able expense,  it  is  a  common  practice  in  such  places  to  place  the 
beets  in  large  pits,  or  else  dig  large  beet-cellars,  which  are  but 
slightly  ventilated.  These  cellars  have  proved  very  useful  in 
cases  where  the  beets  are  placed  in  them  dry  with  but  little  soil 
adhering  and  are  not  stored  too  long. 

The  greatest  foe  of  stored  beets  is  heat,  particularly  moist 
heat.  In  southern  countries,  therefore,  where  the  climate 
remains  warm  throughout  the  sugar-making  period,  it  is  evident 
that  storage  of  the  beets  should  be  avoided  as  much  as  possible. 
But  even  in  localities  where  the  temperature  is  moderate  or  even 
cold,  it  is  possible  for  the  beets  to  become  heated  more  or  less 
strongly,  by  the  heat  of  respiration,  at  places  in  the  heaps  or 
store-houses  where  the  movement  of  the  air  is  restricted  so  that 
they  are  not  cooled  off.  This  trouble  occurs  when  there  are  large 
quantities  of  adhering  dirt  and  when  many  leaves  and  weeds  are 


10  BEET-SUGAR  MANUFACTURE. 

stored  with  the  beets.  Those  places  become  most  heated  where 
the  beets  fall  as  they  are  thrown  in,  and  where  the  dirt  collects 
and  forms  a  mass  with  the  weeds  which  adheres  to  the  beets. 
It  is  advisable,  therefore,  to  watch  the  temperature  by  inserting 
thermometers.  As  soon  as  the  heating  becomes  permanent,  the 
beets  affected  should  be  worked  up  immediately,  if  possible. 

No  matter  how  the  beets  are  stored,  they  are  certain  to  suffer 
more  or  less  change  in  weight,  usually  a  loss.  Only  those  which 
are  affected  by  rain,  dampness  from  the  earth,  or  by  water 
evaporating  from  the  beets  at  the  bottom  of  the  heap,  increase 
in  weight;  and  this  is  noticed  in  particular  when  they  have  been 
pulled  and  transported  in  dry  weather.  In  all  other  cases  beets 
decrease  in  weight.  This  loss  in  weight  is  greater  in  proportion 
to  the  wetness  of  the  weather  during  the  time  of  harvesting  and 
storing,  to  the  completeness  of  the  removal  of  the  atmospheric 
moisture,  to  the  warmth  within  the  heaps,  and  to  the  extent  to 
which  they  are  ventilated. 

The  loss  in  weight  is  greatest  in  cellars  or  heaps  which  are 
ventilated  and  roofed  over,  and  amounts  to  from  5  to  10  per 
cent,  of  the  original  weight.  In  uncovered  heaps  which  are  not 
artificially  ventilated  there  is  either  no  noticeable  change  in 
weight  owing  to  the  action  of  the  weather,  or  there  may  be  even 
a  slight  increase  in  weight.  In  large  heaps  covered  over  with 
earth  there  is  always  a  loss  amounting  to  about  five  per  cent. 

The  sugar-loss  which  the  stored  beets  undergo  is  greater  the 
higher  the  temperature,  the  greater  the  humidity  changes,  and 
the  more  the  ventilation.  In  determining  the  loss  of  sugar  during 
storage,  it  is  absolutely  necessary  to  take  into  consideration  tin- 
change  in  weight  which  the  beets  have  undergone,  or  the  con- 
clusion drawn  may  be  misleading.  The  actual  sugar  loss  in  a 
mild  climate  with  an  average  temperature  of  about  40°  F.  during 
storage  from  the  end  of  October  to  December  amounts  per  day  to 
0.010  to  0.012  per  cent,  in  large  uncovered  heaps,  0.012  to  0.017 
I  XT  cent,  in  ventilated  heaps,  and  0.019  per  cent,  in  large  heaps 
covered  with  earth. 

The  figures  given   above  were  obtained   from   observations. 


THE  DELIVERY,  RECEIVING.  AM)  STORAGE  OF  BEETS.     11 

made  with  uninjured  beets.  Injured  beets  from  which  the  tails 
have  been  broken  off  or  which  have  been  headed  too  much,  and 
in  particular  those  beets  which  have  been  wounded  by  the  prongs 
of  the  fork  or  by  the  knife,  will  show  a  much  greater  sugar  loss. 
They  also  suffer  much  more  from  the  influence  of  mould  and 
diseases  caused  by  phoma,  rhizoctonia,  and  sclerotinia,  which  some- 
times ravage  stored  beets.  At  the  infected  places,  the  flesh  of 
the  beet  becomes  black,  and  the  rotting  penetrates,  in  a  short 
time,  deep  into  the  interior;  so  that  the  beets  become  rotten 
within  a  few  weeks.  Fresh  beets  harvested  from  moist  soil 
usually  prove  more  resistant  than  beets  which  have  become 
wilted  by  prolonged  drought  on  the  field  before  harvesting.  In 
the  last  case  nearly  all  of  the  beets  are  considerably  injured  on 
account  of  the  difficulty  in  pulling  them  out  of  the  ground; 
and,  therefore,  doubly  damaged. 

If  the  beets  grow  during  the  time  of  storage,  it  is  always  a 
sign  that  they  were  laid  away  when  too  warm  and  too  moist. 
The  formation  of  sprouts,  therefore,  is  to  be  traced  to  an  increased 
life-activity,  which  is  naturally  connected  with  a  stronger  respira- 
tion, with  a  greater  change  in  substance,  and  a  greater  loss  in 
sugar.  In  the  sprouting  itself  there  is  only  a  slight  sugar  loss,  for 
these  offshoots  weigh  but  little  compared  to  the  whole  beet,  even 
when  they  have  been  formed  to  a  considerable  extent,  and  the 
sugar  which  they  contain  amounts  to  only  three  or  four  per 
cent,  (sugar  and  in  vert -sugar). 

The  temperature  of  the  stored  beets  depends  chiefly  upon  that 
of  the  outer  air.  Every  lasting  change  in  the  temperature  of  the 
atmosphere  makes  itself  felt  within  the  heap  and  cellars,  naturally 
the  change  taking  place  more  quickly  in  the  uncovered  heaps 
than  in  those  which  are  covered,  and  most  quickly  in  places  ex- 
posed to  the  weather. 

Inasmuch  as  heat  is  evolved  by  the  respiration  of  the  beets, 
it  follows  that  the  temperature  within  the  piles  of  beets  is  greater 
than  the  average  outside  temperature;  this  difference  in  tempera- 
ture of  course  depends  largely  upon  the  amount  of  ventila- 
tion. 


12  BEET-SUGAR  MANUFACTURE. 

During  the  storage  of  beets  there  is  an  increase  in  the  amount 
of  organic  non-saccharine  matter  present  in  the  juice;  because 
sugar  is  decomposed  most,  and  furthermore  certain  insoluble 
portions  of  the  beet  are  transformed  into  soluble  non-saccharine 
matter  which  cannot  be  removed  by  the  processes  of  sugar- 
making. 


CHAPTER  II. 
TRANSPORTING  AND  WASHING  THE  BEETS. 

Conveyance  of  Beets  from  Storage  to  the  Factory. — Formerly 
beets  were  transferred  from  the  places  where  they  were  deposited 
to  the  washing-machines  by  means  of  a  cable  system,  wheel- 
barrows, or  by  baskets,  but  at  present  the  practice  of  using  a 
hydraulic  carrier  has  become  almost  universal.  As  has  already 
been  mentioned,  this  carrier  is  placed  in  the  middle  of  the  storage- 
place,  so  that  by  means  of  properly  arranged  inclined  planes  the 
beets  are  dropped  into  the  stream  of  water  with  the  expenditure  of 
but  little  manual  labor.  These  inclined  planes  are  built  either 
solid  or  as  a  grating.  In  the  latter  case,  a  good  deal  of  the  dry 
dirt  which  adhered  to  the  beets  in  the  form  of  soil  tends  to  drop 
through  on  to  the  ground  beneath,  so  that  the  hydraulic  carrier  will 
contain  less  dirt,  and  less  of  it  will  reach  the  settling-tank.  This 
latticed  platform  is  only  advantageous,  however,  when  the  settling- 
tank  is  small,  and  when  the  dirt  can  be  readily  removed  from 
beneath  the  latticework.  In  wet  weather,  moreover,  the  mud 
adheres  firmly  to  the  beets  and  stops  up  the  spaces  between  the 
grating,  so  that  when  the  beets  are  the  dirtiest,  all  of  the  dirt  will 
be  transferred  to  the  carrier;  consequently  these  latticed  platforms 
can  usually  be  dispensed  with. 

The  hydraulic  carriers  are  usually  laid  at  the  place  where  they 
are  to  be  used,  and  are  as  a  rule  made  of  brick  or  concrete,  smoothly 
finished  on  the  inside,  although  gutters  of  cement  or  iron  are  used 
to  some  extent,  particularly  the  last  when  the  carrier  is  movable. 
Its  vertical  or  inclined  walls  are  at  least  20  to  25  inches  high,  the 
bottom  is  rounded,  and  the  width  is  from  one  to  two  feet  according 

13 


14  BEET-SUGAR  MANUFACTURE. 

to  the  amount  of  beets  to  be  handled.  There  is  a  groove  on  its 
upper  edge  in  which  is  placed  a  covering  for  the  channel  made  of 
wood,  sheet  iron,  or  iron  grating.  With  regard  to  the  fall  which 
the  water  in  the  stream  should  have,  it  is  impossible  to  prescribe 
this  for  all  cases.  As  a  rule,  the  water  should  have  a  fall  of  from 
0  J  to  0.15  inch  per  foot  in  the  straight  portions  and  from  0.15  to  0.20 
inch  at  the  curves.  The  dirtier  the  beets,  the  more  sharp  sand 
and  stones  this  dirt  contains,  the  more  sprouts  the  beets  have,  and 
the  more  careless  the  farmer  has  been  in  removing  the  leaves  and 
weeds,  the  greater  the  waterfall  and  amount  of  water  which  will 
be  necessary. 

In  order  that  the  carrier  may  work  well,  especially  when  it  is  a 
long  one,  it  is  necessary  that  the  beets  should  be  pitched  into  the 
stream  at  one  place,  and  that  the  flow  of  water  should  not  be 
stopped  during  the  passage  of  the  beets.  If  the  water  at  the  out- 
let cannot  run  off  freely,  it  is  necessary  that  the  siphon  arrange- 
ment should  be  capable  of  taking  away  the  water,  even  although 
intermittently,  so  quickly  that  the  water  in  the  channel  does  not 
become  dammed  up.  Every  time  the  stream  of  water  becomes 
dammed  there  is  a  stoppage  of  beets  as  well  as  stones  and  sand, 
and  some  time  elapses  before  the  carrier  acts  normally  again. 

The  water-supply  required  to  operate  the  carrier  depends  in  the 
first  place  upon  the  quantity  of  beets  which  it  is  to  carry.  Less 
than  70  to  100  cubic  feet  per  minute  should  never  be  allowed. 
Ordinary  factories  usually  use  from  140  to  175  cubic  feet  per 
minute;  larger  factories  use  more  correspondingly,  especially 
when  there  are  two  carriers.  More  water  will  be  used,  however, 
in  proportion  as  the  stream  is  wide  and  the  fall  of  the  water  is 
slight.  If  the  supply  of  water  at  the  factoiy  is  limited,  therefore, 
it  is  particularly  important  that  the  width  of  the  stream  and  the 
waterfall  should  be  carefully  regulated.  The  water  used  in  the 
carrier  is  usually  from  the  hot  wells  of  the  condensers.  If  this 
water  is  to  be  used  again  for  factory  purposes  after  it  has  cooled, 
it  -is  necessary  that  it  should  stand  some  time  in  a  settling-tank, 
in  order  to  remove  most  of  the  dirt  taken  up  from  the  beets. 

During  the  time,  whether  long  or  short,  that  the  beets  are  in 


TRANSPORTING  AND  WASHING.  15 

the  warm  water  there  is  bound  to  be  a  certain  amount  of  sugar 
lost,  although  this  loss  is  usually  very  small.  As  an  average  of  a 
great  many  experiments,  it  has  been  found  that  for  100  parts  by 
weight  of  beets  carried  by  water  through  a  channel  about  240 
yards  long  the  loss  in  sugar  will  be : 

with  sound  beets  and  warm  water  (105°-115°F.),  (40°-45°  C.), 
0.02%  to  0.03%,  on  an  average;  at  the  most,  0.05%; 

with  frozen  and  injured  beets  and  warm  water, 
0.1%  to  0.57%,  varying  according  to  the  amount  of  frozen 
and  injured  beets  present. 

Under  ordinary  conditions,  therefore,  the  loss  in  sugar  is  but 
slight,  and  will  not  be  noticeably  lessened  by  making  the  carrier 
shorter  or  using  colder  water.  On  the  other  hand,  the  amount  of 
sugar  dissolved  out  of  frozen  beets  depends  to  a  considerable 
extent  upon  the  length  of  the  carrier  and  the  temperature  of  the 
water.  But  since  it  is  very  difficult  to  float  muddy  beets  which 
are  frozen  together  by  means  of  cold  water,  warm  water  being 
required  to  thaw  them  and  loosen  the  dirt  before  they  can  be 
transported  in  the  carrier,  it  is  evident  that  the  loss  of  sugar  must 
be  regarded  as  unavoidable.  Consequently  the  use  of  cold  water, 
which  has  been  sometimes  recommended,  is  unnecessary  in  the 
case  of  uninjured  beets  and  useless  in  the  case  of  frozen  ones. 

During  the  time  that  the  beets  remain  in  the  water,  both  in 
their  transport  to  the  factory  and  their  washing,  they  take  up  a 
certain  amount  of  water  and  gain  in  weight,  and  of  course  this 
gain  is  more  noticeable  in  the  case  of  dry  and  withered  beets  than 
in  the  case  of  fresh  ones.  The  increase  in  weight,  however,  rarely 
exceeds  \%  to  1%. 

A  contrivance  which  is  very  desirable  and  which  may  be  placed 
in  the  channel  just  before  the  outlet  is  the  sand  and  stone- 
eliminator.  For  this  purpose  machines  of  various  designs  have 
been  constructed.  Stones  and  sand  are  either  removed  by 
placing  a  grating  at  the  bottom  of  the  hydraulic  carrier  above 
which  the  beets  float  by,  and  from  beneath  which  the  deposit 
is  shovelled  away  from  time  to  time;  or  they  sink  into  a  deepen- 


16  BEET-SUGAR  MANUFACTURE. 

ing  in  the  carrier  from  which  an  upward  current  of  water  carries 
the  beets  along.  There  are  also  contrivances  which  remove  the 
floating,  lighter  particles,  such  as  leaves,  straw,  wood,  and  weeds, 
but  these  devices  require  a  uniform  current  in  the  carrier  and 
careful  attention. 

If  the  beets  are  not  stored  in  cellars  which  are  provided  with 
hydraulic  carriers,  the  transportation  of  the  stored  beets  to  the 
washing-machines  is  usually  effected  by  means  of  a  portable 
railway.  In  order  to  cheapen  removal  from  the  ordinary  heaps 
and  silos,  it  is  well  to  make  use  of  portable  hydraulic  carriers 
which  can  be  moved  on  rollers  or  trucks,  when  the  ground  permits, 
so  that  the  beets  can  be  readily  thrown  from  the  heaps  into  the 
carriers. 

The  warm  water  can  best  be  brought  through  open  channels. 
Pipes  are  not  only  expensive,  but  stones  are  likely  to  stop 
them  up. 

Washing  the  Beets. — The  beets  after  reaching  the  factory  at 
once  enter  the  washing-machines  if  these  are  at  low  enough 
levels,  or  are  raised  to  them  by  means  of  suitable  arrangements 
(buckets,  lifting-wheels,  screw  conveyors,  or  chain  elevators)  either 
with  or  without  the  water. 

As  such  apparatus  becomes  more  or  less  worn  from  usage, 
it  has  recently  been  recommended  to  employ  compressed  air 
in  a  similar  way  as  in  the  case  of  the  so-called  "  mammoth  pumps  " 
for  raising  water.  The  contrivance  consists  of  a  wide  U-shaped, 
bent  tube  of  which  one  arm  is  1.5  times  as  long  as  the  other. 
The  beets  flow  into  the  shorter  arm  together  with  water  from  the 
carrier,  and  the  compressed  air  in  the  lower  part  of  the  longer 
tube  makes  the  whole  mass  specifically  lighter,  so  that  it  rises 
in  accordance  with  the  principle  of  communicating  tubes.  Water 
and  beets  flow  upward  into  a  spout  and  from  this  into  the 
washing-machine.  To  prevent  the  tube  becoming  stopped  up 
with  sand  when  not  in  operation,  a  valve  in  the  longer  arm  is 
then  closed,  the  mass  in  the  short  arm  is  kept  in  motion  by  a 
small  amount  of  compressed  air. 

Before  entering  the  washer,  the  beets  should  be  freed  from 


TRANSPORTING  AND  WASHING.  17 

the  carrier-water,  in  order  that  the  dirty  water  shall  not  con- 
taminate the  clean.  It  is  true,  however,  that  impure  water  is 
often  used  for  washing  the  beets,  for  example,  the  water  which 
has  run  off  from  the  diffusers  and  from  the  chip-presses,  or 
filtered  condenser  water;  but  where  there  is  a  plentiful  supply  of 
pure  warm  water  it  is  best  to  use  it,  as  unclean  water  in  the 
washer  is  often  the  cause  of  objectionable  irregularities  in  the 
diffusion,  and  the  beet-juice  is  likely  to  become  contaminated. 
Invariably,  under  all  circumstances,  the  beets  should  be  finally 
washed  off  with  clean  water,  and  where  the  beets  are  washed 
twice,  the  second  washer  should  be  fed  with  pure  water. 

For  washing  it  is  preferable  to  make  use  of  long  agitated 
washers  with  places  for  large  stone  traps.  Drum  washers  are  no 
longer  used  on  account  of  their  inefficiency.  Recently  vertical 
washing-machines  have  been  recommended,  from  which  the  beets 
are  raised  by  a  screw.  These  are  claimed  to  possess  the  advan- 
tage of  completely  removing  the  stones,  straw,  leaves,  and  in 
fact  all  undesirable  impurities,  but  up  to  the  present  time  they 
have  been  but  little  used  in  practice.  A  special  contrivance  on 
the  screw  conveyor  for  the  beets  works  in  a  similar  way  to  this 
washer  in  removing  stones.  Under  the  conveyor  at  the 
bottom  there  is  an  elevated  trough,  at  which  point  the  spirals 
are  replaced  by  some  stirring  arms.  The  stones  fall  between 
these  arms  to  the  bottom  and  are  removed  by  a  conveniently 
placed  manhole. 

Since  the  beets  have  been  freed  by  the  hydraulic  carrier  from 
the  greater  part  of  the  mud  which  adhered  to  them,  it  is  evident 
that  the  washing-machines  do  not  have  quite  so  much  work  to 
do  as  formerly.  At  the  same  time  their  work  remains  of  much 
importance  for  the  succeeding  operations,  especially  in  preventing 
the  choking  the  teeth  of  knives  and  facilitating  the  preparation 
of  good  chips.  Washing,  therefore,  serves  chiefly  to  remove  the 
last  traces  of  dirt  and  the  stones.  The  first  is  accomplished  by 
causing  the  beets  to  collect  in  the  front  part  of  the  washer  so 
that  they  are  obliged  to  rub  up  hard  against  one  another.  In 
the  neighborhood  of  the  stone-eliminator,  however,  there  must 


18  BEET-SUGAR  MANUFACTURE' 

not  be  too  many  beets,  or  the  stones  will  not  settle  so  quickly. 
In  order  to  accomplish  these  ends,  the  principle  to  follow  Ls  to 
have  the  throwing-out  arrangement  of  the  stone-eliminator,  or 
of  that  part  of  the  washer,  capable  of  handling  more  beets  than 
are  brought  into  the  washer.  When  so  constructed,  washers 
work  satisfactorily;  otherwise  the  results  are  never  so  good. 
Arrangements  by  means  of  which  the  lower  mud-holes  open  and 
shut  automatically  at  definite  intervals,  are  desirable,  as  they 
make  the  process  independent  of  manual  labor. 

The  stirring  arms  of  the  washer  are  usually  made  of  wood 
and  are  frequently  so  arranged  as  to  partly  stop  the  progress 
of  the  beets.  They  are  sometimes  fluted  so  that  they  rub  against 
the  beets  more,  or  provided  with  finger-like  side  attachments 
which  collect  weeds  and  leaves. 


CHAPTER  III. 
WEIGHING  AND  SLICING  BEETS. 

THE  beets  are  carried  from  the  washing-machines  by  means  of 
an  elevator  (bucket,  chain,  or  link)  to  the  collecting-bin.  As  beets 
were  formerly  taxed  on  their  weight,  great  stress  was  kid  on 
draining  them  as  much  as  possible  before  weighing.  Nowadays 
less  attention  is  paid  to  this  point;  but  this  is  not  right,  inasmuch 
as  the  water  adhering  to  the  beets  contains  a  great  deal  of  mud, 
sand,  and  bacteria.  The  sand  tends  to  choke  the  teeth  of  the 
knife-blades  and  cutting-plates,  and  eventually  passes  through 
the  diffusers  into  the  mud-pits,  which  require  continual  cleaning. 
The  amount  of  microorganisms  present  during  the  diffusion 
process  depends  on  the  quantity  of  water  adhering  to  the  beets ; 
their  activity  sometimes  becomes  noticeable  and  may  increase 
greatly. 

There  are  numerous  and  various  contrivances  for  weighing  beets. 
A  great  many  factories  do  not  weigh  the  washed  beets  at  all,  but 
consider  the  weight  taken  at  time  of  purchase  as  sufficient,  making 
deduction  for  the  adhering  dirt,  or  else  determine  the  weight  from 
the  contents  of  the  diffusers.  Both  methods  are  thoroughly 
unreliable  and  should  be  discarded;  for  when  the  weight  of  beets 
is  not  known  accurately,  the  first  and  chief  requirement  for  the 
control  of  sugar-yield  is  wanting.  Consequently  every  properly 
conducted  factory  should  accurately  weigh  the  washed  beets. 

As  it  is  usually  difficult  to  obtain  trustworthy  weighers,  auto- 
matic weighing-machines  are  obviously  best,  and  there  are  a  num- 
ber of  these  which  are  perfectly  reliable.  There  are,  however, 
methods  of  checking  the  weights  taken  by  ordinary  scales  with  the 

19 


20  BEET-SUGAR  MANUFACTURE. 

requisite  precision,  so  that  the  latter,  owing  to  their  inexpensive- 
ness,  are  much  in  use. 

The  beets  fall  from  the  weighing-hopper  either  directly  into  the 
slic ing-machine,  or  into  a  collecting-bin  from  which  they  are  raised 
to  the  slicer  by  an  elevator.  Where  space  and  height  are  available, 
the  former  method  is  preferable,  for  it  is  easier  to  keep  the  hopper 
over  the  feeding-discs  full  than  when  the  beets  are  delivered  into 
a  less  readily  accessible  hopper  the  inside  of  which  is  not  visible. 
In  order  to  feed  the  slicer  regularly  when  an  elevator  is  used,  it  lias 
been  suggested  that  the  loading  and  unloading  of  elevator  and 
slicer  be  made  simultaneous  by  an  electric  controller. 

Slicing  the  Beets. — For  slicing  beets  into  "schnitzels,"  or 
"chips,"  beet-slicers  are  used,  based  on  the  well-known  con- 
struction of  a  horizontally  revolving  cutting-plate.  Particular 
stress  is  laid  upon  a  careful  mounting  of  the  machines  so  that  the 
cutting-plate  runs  perfectly.  There  is  a  centrifugal  slicer  made  on 
a  different  principle  which  has  not  come  into  any  extended  use  in 
the  industry.  Recently  a  rotary  drum  slicer  has  boon  invented 
in  which  the  knives  are  placed  on  the  circumference  of  a  drum 
which  turns  on  a  horizontal  axis.  The  beets  fall  through  a 
funnol  on  the  side  into  the  drum  and  are  pressed  against  the 
knives  by  a  horn-shaped  hook.  This  machine  has  great  capacity 
and  makes  very  good  long  slices.  The  customary  horizontal 
machines  differ  essentially  only  in  size  of  cutting-discs  and  arrango- 
mcnt  of  hopper. 

The  cutting-plate  must  be  made  of  the  best  cast  steel  and 
carefully  finished.  Its  diameter  in  German  factories  is  usually 
from  four  to  five  feet,  but  in  other  countries  larger  plates  are  ofton 
used,  sometimes  up  to  eight  feet  in  diameter.  The  smaller  plates 
make  from  100  to  150  revolutions  per  minute,  while  the  largor 
ones  revolve  only  50  times  or  less.  In  general,  it  would  be 
assumed  that  the  larger  plates,  moving  slowly,  would  make  better 
slices  than  the  smaller  ones,  moving  more  quickly;  the  quality 
of  the  slices,  however,  depends  upon  a  great  many  things,  and 
it  is  a  fact  that  in  some  cases  more  satisfactory  slices  arc  obtained 
with  the  smaller  plates  than  with  the  larger  ones.  It  should 


WEIGHING  AND  SLICING  BEETS.  21 

also  be  remembered  that  the  larger  machines  require  more 
time  for  changing  knives  and  removing  stones  which  get  into  the 
machine,  so  that,  unless  extra  machines  are  at  hand,  the  work 
is  likely  to  become  irregular.  It  is,  therefore,  difficult  to  say 
what  sort  and  size  of  plate  is  the  most  desirable. 

The  driving  of  the  beet-slicers  is  almost  always  by  means  of 
belts.  There  are,  however,  machines  which  are  provided  with 
an  independent  steam  or  electric  motor.  The  advantage  of  such 
machines  is  that  the  number  of  revolutions  can  be  changed  more 
readily,  but,  on  the  other  hand,  the  cost  of  installation  is  too 
great  to  permit  their  general  use. 

Above  the  revolving  plate  is  the  cover-piece,  the  construction 
of  which  has  an  important  influence  upon  the  capacity  of  the 
machine.  There  are  two  types  of  cover-pieces;  one  is  con- 
nected with  a  feeding-hopper  so  that  the  beets  press  against  the 
cutting-disc  by  reason  of  their  own  weight,  the  other  type  is 
provided  with  an  arrangement  for  exerting  pressure. 

In  the  former,  the  annular-shaped  feeding-hopper,  which  rests 
upon  this  cover-piece,  must  be  made  so  that  the  beets  slide 
through  it  without  difficulty  and  cover  as  large  a  portion  as  possible 
of  the  plate  in  which  the  knife-holders  rest.  In  the  lower  part  it 
consists  of  two  concentric  jackets,  with  a  break  only  where  the 
knife-holders  are  inserted.  At  the  bottom,  the  breadth  of  this 
hopper  is  a  little  greater  than  the  length  of  the  knife -holders. 
It  is,  however,  not  correct  to  have  both  jackets  of  the  hopper 
built  too  high;  it  is  much  better  if  the  inner  jacket  forms  only  a 
shallow  cap  over  the  centre  of  the  cutting-disc  where  the  shaft- 
bearing  is  situated.  This  cap  consists  of  a  conical  or  smoothly 
rounded  cover,  usually  with  sloping  sides.  The  outer  jacket,  on 
the  other  hand,  is  at  least  1.5  or  2  yards  in  height,  so  that  there 
is  a  good-sized  hopper  into  which  the  beets  fall  freely  and  without 
friction  to  the  mass  below  as  fast  as  the  beets  at  the  bottom  are 
sliced  up  by  the  knives.  On  the  inside  of  the  hopper  or  on  the 
inner  cap  there  should  not  be  anything,  such  as  nuts,  bolts,  or 
rivets,  which  might  interfere  with  the  fall  of  the  beets.  The 
unimpeded  fall  of  the  beets  is  more  important  in  proportion  to 


22  BEET-SUGAR  MANUFACTURE, 

the  speed  of  the  machine,  the  number  of  knife-holders,  and  the 
capacity  of  the  machine  in  general. 

In  order  to  prevent  the  beets  from  turning  with  the  plate  and 
to  keep  them  firmly  in  place  so  that  they  are  properly  sliced  by 
the  knife-blades,  stops  or  counter-knives  are  placed  in  the  cover- 
piece  close  to  the  plate,  so  that  they  come  within  a  few  millimeters 
of  the  highest  part  of  the  blades.  In  the  case  of  a  small  plate,  one 
such  stop  is  sufficient. 

The  stops  are  sometimes  made  movable  and  held  by  steel 
springs  or  counter-weights.  Stones  and  pieces  of  iron  can  thus 
push  through  and  excessive  strains,  which  might  cause  the 
cutting-plate  to  break,  are  avoided. 

For  the  rapid  removal  of  foreign  substances  which  get  into  the 
beet-slicer,  such  as  stones,  pieces  of  iron,  wood,  or  coke,  small 
doors  are  placed  in  the  outer  jacket  opposite  these  stops,  and 
over  these  doors  are  a  number  of  holes  through  which  steel  rods 
can  be  introduced.  As  soon  as  it  becomes  evident  from  a 
peculiar  rattle  inside  the  machine  that  a  hard  foreign  substance 
has  reached  the  knife-blades,  the  machine  must  be  stopped  at 
once,  although  often  before  a  piece  of  iron  or  a  hard  stone  can 
be  removed,  the  knives  or  the  plate  will  break.  Therefore  an 
extra  cutting-plate  must  always  be  on  hand.  At  all  events,  the 
longer  the  foreign  substance  remains,  the  more  knives  will  be 
dulled.  The  obstruction  will  almost  always  be  found  against  a 
stop,  and  it  is  removed  through  one  of  the  above-mentioned  little 
doors.  Steel  rods  are  introduced  through  the  holes  in  order  to 
prevent  the  beets  from  falling  out,  and  the  foreign  substance  is 
usually  under  the  beets  lying  next  to  the  stop.  In  case  the  stone 
cannot  be  found  here,  one  of  the  knife-holders  is  removed  from 
the  plate,  and  the  latter  is  caused  to  make  one  revolution  back- 
wards. This  causes  all  the  beets  and  pieces  of  beets  which  were 
upon  the  plate  to  fall  out  through  the  open  door.  As  it  requires 
considerable  power  to  make  this  backward  revolution,  the  machine 
should  be  fitted  with  an  arrangement  for  this  purpose.  There  arc 
a  number  of  such  which  are  good. 

The  cover-pieces  arranged  to  press  the  beets  down  consist  of 


WEIGHING  AND  SLICING  BEETS.  23 

one  or  several  compartments,  or  channels,  running  in  the  form 
of  a  spiral  over  the  cutting-plate.  The  beets  are  fed  through  a 
common  hopper  into  the  highest  part  of  the  channel  and  are 
carried  along  into  the  narrower  part  by  the  motion  of  the  cutting- 
plate  in  such  a  way  that  the  pressure  channels  are  always  kept 
filled  with  beets  as  far  as  the  stop.  The  beets  are  thus  arranged 
in  a  perfectly  fixed  position  against  the  knives  and  a  uniform  and 
sufficiently  strong  pressure  is  exerted  upon  them  against  the  plate. 
By  this  means  good  chips,  as  free  as  possible  from  mush,  are  pro- 
duced, and  the  capacity  of  the  machine  is  rendered  much  greater. 
A  further  advantage  of  this  construction  lies  in  the  fact  that  it  is 
very  easy  to  remove  foreign  bodies  as  they  invariably  collect  at 
the  narrowest  part  of  the  channel  and  can  be  taken  out  through 
a  trap-door  there.  This  door  can  be  used  also  for  inserting  and 
replacing  the  knife-holders. 

The  number  of  knife-holders  which  are  fitted  into  the  hori- 
zontal plate  varies  greatly.  Aside  from  the  fact  that  a  plate  of 
large  diameter  will  require  more  and  larger  knife-holders  than  a 
smaller  plate,  the  number  of  knife-holders  in  plates  of  the  same 
diameter  depends  upon  whether  the  construction  of  the  plate 
permits  bringing  the  knife-openings  close  together,  or  whether 
the  knife-holders  themselves  are  wide  or  narrow.  Most  knife- 
holders  are  placed  in  a  plate  which  is  strengthened  on  the  under 
side,  so  that  at  the  inner  cutting  circle  the  corners  of  the  holders 
can  almost  touch  one  another  without  materially  lessening  the 
rigidity  and  strength  of  the  plate. 

For  the  plates  most  used  in  Germany,  the  knife-holders  have  a 
length  of  11  inches  clear  and  a  breadth  of  from  3^  to  7  inches. 
Where  larger  plates  are  used,  of  course  larger  knife-holders  are 
necessary.  The  construction  of  these  knife-holders  varies  greatly, 
and  every  year  improvements  are  recommended. 

The  chief  requirements  of  a  good  knife-holder  are : 

1.  It  should  be  made  of  a  good,  hard  material  which  wears 

away  but  little  and  is  not  easily  broken. 

2.  It   should  be   of  solid  construction  without  any  parts 

which  are  easily  worn  out  and  difficult  to  replace. 


24  BEET-SUGAR  MAX  I' I  •  \(  "IT  RE. 

3.  It  should  permit  the  ready  passage  of  the  beet-slices. 

4.  It  should  have  arrangements  for  unscrewing  the  knives 

and  setting  them  at  the  right  height,  and  be  removable 
easily  and  quickly  from  the  plate. 

5.  There  should  be  an  arrangement  for  placing  the  holder 
in  the  correct  position,  so  that  the  knife  has  the  right 

slope. 

6.  The  holder  should  exactly  fit  into  the  openings  in  the 

plate  so  that  there  will  be  no  exposed  edges  or  corners 
at  any  place. 

If  the  knife-holders  fulfil  the  above  requirements,  it  is  a  matter 
of  indifference  how  they  are  made;  the  simpler  they  are,  the  better 
for  practical  work.  Holders  which  fill  some  one  of  the  above  condi- 
tions particularly  well  and  which  are  specially  praised  with  regard 
to  that  one  particular  should  be  carefully  examined  to  see  whether 
they  satisfy  the  other  conditions  as  well,  which  is  frequently  not 
the  case. 

For  fibrous  beets,  or  to  prevent  small  stones  from  getting  into 
the  machine  with  the  beets,  guards  have  been  tried  the  front  edges 
of  which  do  not  run  parallel  with  the  knives,  but  are  hollowed 
out  so  that  only  thin  points  reach  close  up  to  the  blades.  These 
points  are  sufficient  for  holding  the  beets,  but  let  the  fibres,  and 
particularly  the  small  stones,  fall  through  the  openings  before 
striking  the  knives. 

The  knife-holder  must  exactly  fit  into  the  plate,  for  every 
projection  on  the  side  or  upon  the  surface  of  the  plate  against 
which  the  beets  strike,  throws  them  out  of  their  correct  position, 
the  result  being  bad  slices.  Consequently  now  knife-holders  will 
not,  as  a  rule,  fit  old  plates,  for  the  latter  are  usually  somewhat 
worn  away  by  use.  For  the  same  old  holders  are  not  suitable 
for  new  plates. 

The  knives  which  are  used  for  the  smaller  plates  are  always  5£ 
inches  long,  so  that  two  of  them  can  be  screwed  into  one  holder. 
The  width  of  the  knife  is  detenu ii KM!  by  that  of  the  holder,  and  its 
thickness  is  from  }  to  J  inch.  The  different  kinds  of  knives  now 


WEIGHING  AND  SLICING  BEETS.  25 

in  use  may  be  divided  into  three  classes:  " Dachrippen,"  Konigs- 
felder,  and  Double  knives. 

The  Dachrippen,  or  ridge  knives  have  the  advantage  of  great 
efficiency  because  the  beets  are  sliced  with  a  single  cut.  They 
are  made  in  very  different  forms;  the  number  of  the  roof-shaped 
ridges  varies  from  twenty  to  forty  to  the  knife,  so  that  they 
are  from  J  to  i  inch  apart,  and  the  slices  are  of  the  same  breadth. 
They  are  made  by  grinding  steel  plates. 

The  Konigsfelder  knives  make  only  half  a  cut  at  a  time.  Their 
ridges  are  £  to  i  inch  apart.  It  is  much  easier  to  sharpen  them 
and  they  are  not  so  readily  covered  with  fibres  as  the  former. 
They  are  either  cut  from  steel  plates  or  rolled  from  sheet  metal. 

If  either  of  the  above-mentioned  kinds  of  knives  be  correctly 
placed  in  the  revolving  plate,  only  grooved  slices  will  be  obtained 
if  the  beets  are  held  still  while  being  sliced.  The  correct  position 
of  the  Dachrippen  knives  is  when  all  the  cutting  edges  are  placed 
in  exactly  concentric  circles,  while  with  the  Konigsfelder  knives 
the  cutting  edges  of  all  the  odd  cutting-blades  should  be  con- 
centric with  the  grooves  of  the  even  ones.  As  a  matter  of  fact 
this  correct  position  is  never  attained,  and  consequently  there 
will  always  be  found  mixed  with  the  grooved  slices  others  of  all 
sorts  of  cross-sections. 

Since  it  is  important  for  the  uniform  extraction  of  the  beets 
that  the  slices  should  be  as  uniform  in  cross-section  as  possible, 
the  so-called  "double  knives"  have  come  into  quite  extensive  use, 
by  means  of  which  triangular  slices  are  obtained.  These  knives 
are  placed  in  a  holder,  or  else  in  two  successive  holders,  in  such 
a  way  that  a  "  Dachrippen  "  or  Konigsfelder  knife  is  immediately 
followed  by  a  straight  knife.  The  first  knife  makes  a  triangular 
slice  and  the  next  knife  cuts  straight  through  and  also  makes  a 
second  triangular  slice.  By  this  arrangement  slices  of  more 
uniform  cross-section  are  obtained  than  with  any  other  knives, 
but  their  shape  is  less  suited  for  good  and  rapid  diffusion  working. 

On  the  whole  it  is  impossible  to  recommend  unhesitatingly  one 
form  of  knife  over  another.  Equally  good  results  can  be  obtained 
with  all  three  types  if  the  necessary  care  is  taken  in  sharpening 


26  BEET-SUGAR  MANUFACTURE. 

and  tempering  and  placing  them  correctly  in  the  holder  opposite 
to  the  counter-blade.  The  knives  are  usually  sharpened  by 
means  of  bevelling-  and  sharpening-machines,  of  which  there  are 
many  of  suitable  construction,  but  the  blades  should  always  be 
finished  by  means  of  a  fine  file  in  order  to  obtain  a  perfectly 
even  cutting  surface. 

One  of  the  chief  requirements  for  good  slices  is  that  the  beets 
should  be  well  washed  and  free  from  stones  when  they  reach  the 
beet-slicer.  This  requirement  is  frequently  not  met,  and  where 
complaint  is  made  that  the  slices  are  bad  it  is  usually  best  to  make 
the  washing  better  and  more  thorough  rather  than  try  different 
experiments  with  knives  and  knife-holders  of  all  sorts.  Good 
slices  are  essential  for  good  work  in  diffusion,  so  that  even  when 
it  is  necessary  to  make  costly  improvements  in  the  wash-house, 
the  cost  is  usually  repaid  by  the  increased  efficiency  of  the  plant. 

The  condition  of  the  beets  and  their  inner  structure  naturally 
has  an  important  influence  on  the  quality  of  the  slices.  It  is  not 
possible  even  with  the  best  machinery  to  obtain  perfectly  satis- 
factory chips  from  beets  with  a  hard  and  fibrous  tissue,  particu- 
larly when  they  have  been  pulled  after  having  gone  to  seed. 
The  same  is  true  of  rotten  beets  or  those  with  the  meat  too 
soft.  It  is  also  impossible  to  prepare  good  slices  when  too  many 
weeds  and  leaves  are  mixed  with  the  beets,  as  there  has  never 
been  any  machine  invented  which  is  certain  to  catch  these  before 
the  slicing-machine  is  reached.  The  knives  soon  begin  to  dull 
and  more  or  less  pulp  becomes  mixed  with  the  chips.  This 
difficulty  has  recently  become  more  pronounced  because  of  the 
inability  of  the  farmer  to  obtain  enough  efficient  labor  to  clean 
the  fields  and  harvest  the  crop. 

The  beets  are  discharged  from  the  slicing-machines  either  into 
trucks  or  barrows,  or,  what  is  more  common,  they  are  carried  to 
the  diffusers  by  mechanical  contrivances  (belt,  screw,  bucket,  or 
the  favorite  rope  conveyors). 


CHAPTER   IV. 
EXTRACTION   OF   THE   JUICE. 

THE  sugar-beet  consists  of  cellular  tissue  traversed  length- 
wise by  vascular  tissue  and  surrounded  at  the  surface  by  epidermal 
cells.  The  cells  have  very  different  shapes,  varying  from  globular 
to  an  elongated  form;  they  are  surrounded  on  all  sides  by  a 
membrane,  the  cell-wall,  upon  which  the  primordial,  or  proto- 
plasmic, utricle  rests;  within  the  latter  is  found  the  cell-contents 
and  cell-nucleus. 

The  size  of  the  cells  varies  greatly;  in  the  round  forms,  the 
diameter  averages  about  0.04  mm.  and  the  volume  0.000,033  cubic 
millimeters.  The  walls  of  the  separate  cells  grow  together  and 
increase  in  thickness  as  the  beet  grows.  The  substance  thus 
formed  is  called  the  intercellular  substance.  On  account  of 
the  different  shapes  of  the  cells,  the  growth  of  the  cell -wall  does 
not  take  place  in  all  places,  but  a  great  many  hollow  spaces  are 
formed  between  the  cells,  the  so-called  intercellular  spaces, 
which  are  rilled  with  air. 

It  is  impossible  for  juice  to  pass  out  from  a  living  cell,  because 
the  protoplasmic  utricle  is  practically  impenetrable  by  the 
cellular  juice.  Therefore,  the  object  of  all  juice-extraction 
processes  is  first  to  destroy  the  utricle,  or  to  so  change  it  that 
it  no  longer  hinders  the  passage  of  the  juice. 

The  destruction  of  the  cells  by  mechanical  means  (grinding) 
has  long  since  been  abandoned.  It  is  now  the  general  practice 
to  take  advantage  of  the  effect  of  heat  upon  the  protoplasmic 
utricle.  If  the  cells  are  heated  to  temperatures  above  55°-60°  C. 
(130°-140°  F.),  the  utricle  is  detached  from  the  cell-wall  so  that 
only  the  latter  surrounds  the  cell-contents  on  all  sides.  This 
wall  consists  of  a  very  thin  and  penetrable  membrane,  being 

27 


28  BEET-SUGAR  MANUFACTURE. 

especially  thin  at  the  guttated  places.  The  juice  can,  therefore, 
easily  pass  out  from  a  cell  which  is  altered  by  heat  or  "killed," 
and  be  obtained  by  expressing  or  diffusion. 

Therefore,  all  of  the  present-day  methods  for  obtaining  beet- 
juice  first  exposes  the  sliced  beets  to  temperatures  of  at  least 
60°-70°  C.  (140°-158°  F.),  and  in  fact  this  is  usually  brought  about 
by  mixing  them  with  hot  juice  previously  extracted.  For  the 
killing  of  the  cells,  it  is  immaterial  whether  this  heating  takes 
place  slowly  or  rapidly  and  whether  the  temperature  is  70°, 
90°,  or  100°  C.  Hence,  the  manner  and  degree  of  the  heating  is 
determined  by  other  considerations. 

A.  DIFFUSION. 

In  processes  based  upon  juice  extraction  by  diffusion,  the 
sliced  beets  are  first  of  all  heated  by  means  of  hot  juice,  and 
slowly  lixiviated  with  water  in  a  systematic  manner.  It  is  not 
yet  entirely  clear  as  to  what  takes  place  in  the  cells  themselves ; 
it  is  not  known  whether  the  cell-wall  is  everywhere  a  closed 
membrane,  whether  it  is,  therefore,  a  question  of  osmotic  processes 
in  the  separate  cells,  or  merely  a  case  of  simple  lixiviation. 
The  fact  is  that  the  sugar,  although  it  belongs  to  the  class  of 
difficultly-diffusible  substances,  passes  readily  and  rapidly  from 
the  "killed"  cells  into  the  surrounding  water,  or  into  aqueous 
solutions. 

In  the  beet  chips,  however,  there  are  only  relatively  few 
cells  at  the  surface  to  come  into  immediate  contact  with  the 
extracting  liquid.  The  majority  of  the  cells  are  in  the  interior 
and  the  juice  within  them  must  pass  through  other  cells  and 
through  the  intercellular  spaces;  the  latter  are  partly  connected 
with  one  another  and  form  harrow  canals  in  the  intercellular 
substance.  Such  movements  of  juice  in  the  cell-ducts  are  brought 
about  by  diffusion,  and  follow  the  laws  which  govern  diffusion 
processes  between  liquids,  or  solutions,  that  are  in  immediate 
contact  with  one  another  without  any  separating  membrane. 
The  rapidity  of  such  a  diffusion  is  dependent  chiefly  upon  the 


EXTRACTION   OF  THE  JUICE.  29 

size  of  the  surfaces  in  contact  with  one  another,  upon  the  degree 
of  concentration  and  the  differences  in  the  amount  of  dissolved 
substance  present  in  the  layers  of  liquid,  and  finally  upon  the 
temperature. 

Beside  these  diffusion  processes,  which  included  the  processes 
of  a  more  or  less  osmotic  nature  that  take  place  at  the  cell- 
walls,  there  is,  furthermore,  a  washing  away  of  the  cell  juice  from 
those  cells  which  were  injured  during  the  slicing  of  the  beets. 
Those  cells  that  came  into  direct  contact  with  the  knives  are 
left  open;  the  number  of  such  cells  varies  with  the  thickness 
of  the  slices  and  amounts  to  from  two  to  five  per  cent,  of  all 
the  cells.  The  cell  layers  lying  directly  beneath  are  sometimes 
more  or  less  injured  by  the  pressure,  and  more  or  less  smashed, 
but  most  of  them  remain  uninjured. 

Finally,  there  are  substances  contained  undissolved  in  the 
beets,  that  dissolve  more  or  less  quickly  in  hot  water,  during 
the  work.  In  a  properly  conducted  diffusion  process  the  aim  is 
to  prevent  and  restrict  all  such  action  as  much  as  possible. 

For  carrying  out  the  diffusion  a  battery  of  connected  lixiviat- 
ing vessels  or  diff users  is  used.  The  number  of  diff users  in  such 
a  battery  varies  from  six  to  sixteen.  The  smaller  number  is 
found  in  the  so-called  "  shortened  "  or  "  divided  "  batteries  which 
are  worked  with  a  very  hot  and  slow  current  of  juice,  whereas 
the  larger  number  occurs  in  those  which  are  worked  at  a  lower 
temperature  and  with  a  more  rapid  juice  circulation.  As  a  rule, 
most  batteries  in  use  to-day  contain  from  ten  to  fourteen  diffusers 
arranged  in  a  straight  line,  and  when  more  than  ten  in  num- 
ber in  two  columns  for  convenience  of  supervision  and  labor. 
The  circular  diffusion  batteries,  with  the  slicing-machine  in  the 
centre,  which  were  formerly  preferred,  are  not  now  built  in 
Germany,  although  it  is  most  convenient  to  look  after  and  feed 
the  cells  in  such  an  arrangement.  The  disadvantages  are  that 
more  space  is  required,  and  it  is  difficult,  as  well  as  expensive,  to 
combine  two  such  batteries  with  a  common  arrangement  for 
transporting  and  slicing. 

The  form  and  capacity  of  the  diffuser  also  vary  much.     The 


30  BEET-SUGAR   MANUFACTURE. 

capacity  varies  from  500  to  2600  gallons,  although  at  present  a 
capacity  of  from  1300  to  2100  gallons  is  preferred.  The  quite 
small  diffusers  which  were  formerly  in  use  in  Austria  on  account 
of  the  government  tax  levied  there  (some  with  only  a  capacity  of 
40  gallons)  have  been  discarded  as  being  absolutely  unpractical. 
But,  on  the  other  hand,  too  large  vessels  are  often  undesirable, 
particularly  when  the  amount  of  boots  to  be  handled  doos  not 
correspond  to  the  size  of  the  diffusers  anil  when  the  slices  are  not 
very  good  or  too  fine. 

The  shape  of  the  diffuser  should  be  such  as  to  insure,  as  far  as 
possible,  a  good  and  equal  extraction  at  all  places  in  the  diffuser, 
but  without  hindering  the  passage  of  the  liquor.  Both  require- 
ments, however,  cannot  be  met  equally  well.  With  regard  to  the 
shape  of  the  diffuser,  first  of  all  the  relation  of  its  diameter  to  its 
height  must  be  considered.  Naturally  the  extraction  of  the  beet- 
juice  is  better  the  higher  the  vessel  and  the  less  its  diameter.  But 
as  the  height  of  the  space  which  is  filled  with  beet-chips  and  through 
which  the  juice  has  to  flow  increases,  the  greater  the  resistance 
which  the  flow  has  to  overcome.  Further,  when  the  diameter  is 
small  the  size  of  the  strainer  in  the  bottom  is  restricted,  so  that 
the  holes  become  partly  covered  with  beet-chips  and  the  passage  of 
the  juice  is  much  impeded. 

Experiments  have  been  made  to  ascertain  what  should  be  the 
relation  between  the  height  and  diameter  of  the  diffuser.  Speci- 
fications of  general  application  cannot,  however,  be  given,  for  the 
resistance  to  the  passage  of  the  diffusion-juice  depends  not  only 
upon  the  length  of  travel  in  a  single  diffuser,  but  also  upon  the 
number  of  cells  in  a  batten-,  upon  the  size  of  the  free  passage 
beneath  the  sieve  bottom,  upon  the  thickness  and  character  of  the 
beet-chips,  and  upon  the  way  these  act  during  the  diffusion,  par- 
ticularly on  being  heated.  The  last  two  conditions  are  different 
in  every  factory  and  do  not  remain  constant  in  the  same  house, 

that  it  is  clear  that  for  every  change  in  the  method  of  work- 
ing quite  different  relations  must  be  maintained. 

At  the  same  time  there  are  certain  principles  which  should 
govern  the  choice  of  most  diffusers.  With  very  thin  beet-chip-, 


EXTRACTION"   OF   THE  JUICE.  31 

it  is  preferable  to  choose  low  vessels  of  large  diameter.  With 
thicker  slices,  the  height  of  the  diffuser  should  be  greater  and  its 
diameter  less.  For  the  ordinary  methods  of  working  and  average- 
sized  diffusers,  cylindrical  vessels,  with  a  relation  of  diameter  to 
height  of  1:1}  to  1:H,  are  usually  preferred.  The  ratio  1:2  is 
only  seldom  met  with,  for  on  the  whole  it  is  preferable  to  increase 
the  number  of  cells  in  a  battery  rather  than  to  exceed  the  relation 
1:1}. 

What  has  just  been  said  applies  to  the  vessels  which  are 
cylindrical  from  top  to  bottom.  This  form,  for  various  reasons, 
has  not  always  been  chosen.  Experiments,  which  will  be  men- 
tioned again  later  on,  have  shown  that  the  extraction  at  different 
places  in  the  diffuser  is  likely  to  be  very  different.  It  was 
thought  that  this  could  be  remedied  by  changing  the  form  of 
tho  vessel,  and  in  fact  conical-shaped  vessels  have  been  devised 
and  tried.  It  is  not  probable,  however,  that  the  form  of  the 
diffuser,  unless  it  is  very  abnormal,  exerts  much  influence  upon 
the  juice  extraction;  consequently  such  deviations  from  the 
cylindrical  forms  have  been  abandoned. 

The  shape  of  the  upper  and  lower  part  of  the  diffuser  is  con- 
ditioned by  the  manner  of  filling  and  discharging.  The  upper 
part  must  be  made  so  that  the  slices  can  be  introduced  easily 
and  uniformly.  The  opening  for  filling  and  the  neck  of  the 
diffuser  should,  therefore,  be  as  large  as  possible,  and  the  conical 
parts  connected  with  it  should  not  be  too  flat. 

If  the  cell  is  emptied  through  manholes  on  the  side,  the  lower 
part  is  usually  cylindrical;  the  lower  strainer  is  then  flat  and 
is  of  same  diameter  as  the  cell  itself.  Some  cells,  however,  are 
made  with  the  lower  part  opposite  the  manhole  side  rounded  so 
as  to  facilitate  the  removal  of  the  exhausted  pulp.  Recently 
diffusers  have  been  built  with  a  mechanical  emptying  contrivance, 
the  lower  part  of  which  is  shaped  like  a  trough.  In  the  trough 
is  placed  a  screw  which  pushes  the  spent  chips  out  through  the 
manhole  at  the  further  end.  The  screw  is  set  in  motion,  as  soon 
as  the  manhole  is  opened,  by  toothed  wheels  that  are  placed  outside 
the  diffuser  at  the  further  end.  In  all  cases  when  there  is  side 


32  BEET-SUGAR   MANU1  ArTFRE. 

discharge,  it  is  advisable  to  provide  a  valve  for  introducing 
water  into  the  lower  part  of  the  diffuser  on  the  side  opposite  to 
the  manhole.  Such  a  valve  is  opened  simultaneously  with  the 
discharge-gate.  This  washing-out  process,  however,  works  only 
when  there  is  an  abundant  supply  of  water,  so  that  it  is  advisable 
to  save  the  waste  water  for  this  purpose,  collecting  it  in  tanks. 

In  the  case  of  diffusers  with  bottom-discharge,  the  lower  part 
is  cylindrical  if  the  gate  is  of  the  same  diameter  as  the  cell;  other- 
wise it  is  conical,  tapering  to  the  size  of  the  gate.  The  sieves 
of  this  bottom-discharge  type  rest  on  the  gate,  or  in  the  coned- 
bottomed  ones  follow  the  shape  of  the  cone.  In  the  latter  form, 
it  is  very  effectual  to  make  the  holes  in  the  upper  part  of  the 
conical  sieve  smaller  or  spaced  more  than  in  the  lower  part. 
When  the  gate  is  of  large  diameter,  difficulties  are  often  encoun- 
tered if  ordinary  rubber  rings  are  used  to  make  a  tight  joint. 
It  is  better,  therefore,  to  use  rubber  hose,  so  that  when  the  cover 
sticks,  steam  or  water  pressure  can  be  introduced  through  the 
hose  and  the  cover  raised. 

It  is  very  convenient  to  have  the  lower  gates  arranged  to 
open  and  close  from  above. 

Whatever  their  form,  after  the  cells  have  been  connected 
together  to  form  a  diffusion  battery,  the  chief  requirement  is  to 
have  the  diffusion-juice  pass  through  as  completely  and  un- 
hindered as  possible. 

The  following  means  are  employed  to  improve  circulation : 

1.  Increasing  water-pressure  on  last  diffuser. 

2.  Lessening  back  pressure  from  the  measuring-tank. 

3.  Increasing  diameter  of  pipes  and  valves. 

4.  Removing  completely  all  air  accumulated  in  apparatus. 

5.  Increasing  the  free  openings  of  bottom  sieves. 

In  most  cases  the  most  effectual  change  is  made  by  enlarging 
the  free  openings  of  the  strainer  in  the  bottom.  It  is  not  sufficient 
to  have  the  area  a  few  times  larger  than  the  discharge-pipe,  because 
the  chips  lying  directly  on  the  sieve  cover  or  clog  up  most  of  the 
holes,  especially  if  these  chips  are  fine  or  soft.  Hence  the  area  of 


EXTRACTION   OF  THE  JUICE.  33 

the  sieve  should  be  the  greatest  possible,  and  those  strainers  are 
best  which  have  the  largest  number  of  holes  or  slits  of  appropriate 
size  and  yet  possess  the  necessary  strength  to  support  the  weight 
of  the  chips. 

Formerly  strainers  were  often  placed  in  the  upper  neck  of  the 
cell,  but  have  been  discarded  as  not  only  useless  but  harmful, 
since,  being  of  small  size,  they  impede  the  flow  of  juice  just  as 
soon  as  chip  fragments  from  the  preceding  cells  have  stopped  up 
the  holes. 

Increasing  the  water-pressure  on  the  last  cell  is  usually  of 
doubtful  expediency  when  the  ordinary  head  between  water-tank 
and  measuring-tank  is  increased  over  30  feet.  According  to  the 
familiar  law,  the  velocity  of  the  flow  increases  only  in  proportion 
to  the  square  root  of  the  pressure.  Moreover,  every  time  the 
water-pressure  is  increased,  the  pressure  on  the  strainer  is  in- 
creased also.  If  the  chips  are  firm  and  hard,  this  does  no  par- 
ticular harm,  but  if  the  chips  are  soft  and  fine,  this  increased 
water-pressure  is  likely  to  make  trouble.  Therefore  this  remedy 
fails  when  it  is  most  needed. 

It  is  also  wrong  to  allow  a  pump  to  act  directly  on  the  diffusion 
circulation,  for  besides  the  excessive  pressure,  pulsation  of  the 
pump  acts  injuriously.  Centrifugal  pumps  are  less  objectionable, 
as  the  pressure  is  more  even. 

Likewise,  reducing  the  back  pressure  of  the  measuring-tank 
by  putting  a  pump  in  the  pipe-line  between  the  battery  and  the 
tank  is  efficacious  only  in  special  cases.  Further,  this  can  make 
trouble  by  sucking  air  into  the  cells,  if  the  suction  is  too  strong. 
For  the  same  reason,  but  more  on  account  of  complication  and 
expense,  it  is  impracticable  to  put  centrifugal  pumps  on  the 
overflows  from  every  cell. 

Attempts  have  been  made  to  relieve  the  pressure  of  the  chips 
on  the  strainers  by  hanging  wooden  beams  or  gratings  from  chains 
inside  the  cell,  so  as  to  take  some  of  the  weight.  This  has  met 
with  some  success,  but  the  difficulty  of  discharging  spent  chips  is 
so  increased  that  these  contrivances  are  only  made  use  of  in 
emergencies,  as,  for  instance,  in  working  up  frozen  or  damaged  beets. 


34  BEET-SUGAR   MANUFACTURE. 

The  bad  effect  of  large  amounts  of  air  upon  the  juice 
circulation  is  explained  by  the  fact  that  the  juice  goes  from  top 
to  bottom,  while  the  air  tends  to  rise.  Consequent!}',  when  a 
large  quantity  of  air  or  vapor  is  present,  especially  when  it  is 
distributed  between  the  chips  throughout  the  whole  diff user,  the 
circulation  of  juice  has  to  overcome  great  resistance.  For  the 
removal  of  accumulations  of  air  and  vapor,  blow-off  cocks 
may  be  provided  in  the  upper  part  of  each  cell,  preferably 
automatic  ones.  Under  normal  conditions,  when  only  water- 
pressure  is  used,  blow-off  cocks  are  unnecessary.  If  the  juice  in 
the  last  cell  is  forced  out  by  compressed  air,  however,  it  c:m 
happen  that,  through  leaky  valves,  some  of  the  air  gets  into 
the  other  cells.  In  this  case,  apparatus  for  automatically  remov- 
ing air  and  vapors  is  very  useful,  likewise  when  gases  a>v  evolved 
from  the  chips  during  diffusions. 

Whether  the  circulation  is  satisfactory  or  not,  it  is  advisable' 
in  all  cases  to  have  pressure-gauges  at  each  overflow.  By  this 
means  the  pressures  prevailing  throughout  the  battery  are  always 
known,  and  it  can  be  seen  at  a  glance  where  the  pressure  is  most 
diminished  and  hence  where  the  flow  is  meeting  with  most 
resistance. 

Pipes  and  valves  of  large  cross-section  are  excellent,  but  in 
many  cases  their  advantage  has  been  exaggerated.  If  the  velocity 
of  the  current  in  the  pipes  is  not  greater  than  3  to  3-V  feet  per 
second,  there  is  not  much  use  in  enlarging  them,  for  poor  pressure 
must  then  result  from  other  cause. 

For  warming  the  juice  as  it  passes  from  one  cell  to  another. 
juice-heaters,  or  "calorizators,"  are  used,  or  this  is  effected  In- 
direct steam  injection.  In  general  the  juice-heater  is  to  be  pre- 
ferred, for  in  this  case  the  juice  can  be  heated  with  exhaust -steam 
at  low  pressure,  so  that  the  process  is  not  so  expensive  as  in  direct 
heating,  for  the  latter  uses  live  steam  coming  directly  from  the 
boilers.  However,  the  objection  which  has  been  raised  against  this 
method  of  direct  heating,  that  it  makes  the  final  juice  thinner  on 
account  of  the  water  condensed  in  it.  has  not  been  verified  by 
experiment.  Unquestionably  all  of  the  steam  is  condensed  so  that 


EXTRACTION   OF   THE   JUICE.  35 

the  outflowing  juice  will  be  diluted,  but  as  the  juice  meets  with 
fresh  chips  in  the  last  cell  and  is  not  warmed  subsequently,  this 
dilution  is  not  perceptible  in  the  final  concentrate.  Again,  it 
should  not  be  overlooked  that  even  juice-heaters  have  a  bad  influ- 
ence on  the  density  of  the  juice.  Juice  becomes  more  concentrated 
in  the  process  of  diffusion  in  proportion  to  the  space  taken  by  the 
chips  in  the  cell,  and  less  so  in  proportion  to  the  space  filled  with 
juice  alone;  hence  spaces  which  simply  contain  juice  are  wasted 
as  far  as  diffusion  is  concerned,  and  the  space  taken  by  juice- 
hoaters  must  be  so  considered.  Moreover,  juice-heaters  some- 
times have  the  disadvantage  of  causing  loss  by  leakage;  hence 
this  loss  is  prevented  by  direct  steam-heating. 

In  order  to  economize  the  steam  used  in  diffusion,  warm  water 
is  often  used  for  obtaining  pressure.  For  this  purpose  the  water 
coming  from  the  condenser  hot-wells  or  the  condensation-water 
from  the  evaporators  is  used,  or  that  from  special  heaters  warmed 
by  the  vapors  from  the  evaporators  and  hence  at  no  expense. 

This  water  is  usually  warmed  not  more  than  40°-50°  C. 
(100°-120°  F.),  but  can  be  hotter,  if  the  cells  have  bottom 
discharge  or  are  emptied  by  use  of  compressed  air. 

If  the  spent  chips  are  not  to  be  dried  but  immediately  used  as 
fodder  or  put  in  silos,  it  is  absolutely  necessary  that  they  be  cooled 
before  pressing,  since  chips  pressed  while  hot  spoil  quickly. 

In  this  case  two  water-pipes  are  supplied  so  that  the  chips  can 
be  mashed  with  warm  water  and  pressed  out  with  cold,  and,  in 
some  cases,  finally  rinsed  with  more  cold  water. 

The  Method  of  Working  a  Diffusion  Battery  is  different  in 
almost  even-  factor)*.  The  only  common  features  in  the  different 
methods  are  the  routine,  the  almost  invariable  heating  of  the  juice  as 
it  passes  from  one  cell  to  the  next,  and  the  manner  of  circulation. 
The  juice  runs  from  top  to  bottorn  in  all  cells  except  in  the  one  which 
has  just  been  charged  with  chips,  and  which  is  filled  from  the 
bottom  to  expel  air.  With  regard  to  everything  else  the  process 
varies  within  pretty  wide  limits,  particularly  as  to  temperature, 
time  of  treatment,  and  density  of  juice.  Since  the  number  and 
size  of  cells  in  the  batten*  as  well  as  the  properties  of  beets  and 


36  BEET-Sl'Cl AR  MANUFACTURE. 

chips  are  very  different,  it  is  quite  impossible  to  define  any 
standard  method  of  operation.  Therefore  directions  applying 
generally  can  never  be  given,  but  only  such  fundamental  prin- 
ciples stated  as  will  help  in  working  out  the  most  favorable  con- 
ditions for  each  factory. 

The  first  condition  for  good  diffusion  work  is  to  have  water 
as  pure  as  possible,  soft  and  quite  free  from  soluble  impurities. 
Hard  spring  water  retards  somewhat  the  extraction  in  the  last 
difTuser,  but  is  otherwise  quite  suitable,  inasmuch  as  most  of 
the  lime  salts  are  removed  during  the  carbonatation.  Where 
good  water  cannot  be  obtained,  the  strength  and  purity  of  the 
diffusion-juice  always  suffers,  particularly  when  factories  have 
to  use  purified  waste  water  from  the  settling-tanks  for  the 
diffusion;  such  water  always  contains  soluble  mineral  and  organic 
matter.  All  these  substances  are  not  removed  during  the  puri- 
fication of  the  juice  any  more  than  are  the  alkali  salts  in  river- 
water  which  has  been  contaminated  with  brine  and  yet  has 
to  be  used  in  certain  factories;  they  contaminate  the  products 
of  the  factory  and  lessen  the  yield  in  proportion  to  the  amount 
of  juice  that  is  drawn  off,  or,  in  other  words,  the  more  water  there 
is  present  in  the  juice. 

If  only  a  limited  supply  of  pure  water  is  at  the  disposal  of 
a  sugar-factory,  the  amount  of  juice  should  be  kept  as  small 
as  possible  and  the  water  piping  for  the  diffusion-water  must  be 
connected  by  means  of  special  valves  both  with  the  pure  water- 
pipes  and  also  with  the  pipes  containing  the  water  that  is  ordi- 
narily used  in  the  factory.  The  pure  water  is  then  used  for  the 
mashing  of  the  chips,  as  this  water  alone  gets  into  the  juice, 
whereas  the  impure  water  is  used  for  pressure  purposes  and 
can  be  removed  from  the  diffusion  on  emptying  the  cells.  Instead 
of  using  water,  compressed  air  can  be  utilized.  In  the  last  case, 
the  removal  of  the  dry  spent  chips  is  attended  with  difficulty 
except  when,  in  bottom  discharge,  the  lower  manhole  has  the 
same  diameter  as  the  difTuser. 

A  diffusion  which  is  satisfactory  effects  good  extraction  from 
the  slices,  and  yields  juice  which  is  of  the  greatest  possible  con- 


EXTRACTION   OF  THE  JUICE.  37 

ccntration.  The  diffusion  process  is  not,  as  has  already  been 
explained,  and  what  was  first  assumed  when  this  method  of 
sugar-extraction  was  introduced,  a  simple  diffusion  action,  but 
at  the  same  time  there  is  a  lixiviation  as  well. 

Even  with  very  smooth  chips  many  of  the  plant-cells  are 
broken,  and  the  proportion  of  these  broken  cells  increases  with 
the  fineness  of  the  chips.  With  ordinary,  more  or  less  rough, 
chips  the  number  of  broken  cells  is  still  greater,  and  from  such 
cells  the  contents  are  simply  washed  away.  Furthermore,  the 
cell-walls  and  the  intercellular  substance,  as  well  as  certain  solid 
substances  contained  in  the  cells,  are  partly  dissolved  by 
long-continued  action  of  the  water.  This  is  particularly  true  of 
pectic  substances  and  organic  calcium  and  potassium  salts. 

While  the  beet-slices  are  under  treatment  in  the  diffusion 
battery,  three  different  processes  are  taking  place  simultaneously 
namely : 

1.  The  forcing  of  juice  out  of  broken  cells. 

2.  The  dialysis  of  the  soluble  constituents  contained  in  the 

killed  but  uninjured  cells. 

3.  The  gradual  solution  of  the  difficultly  soluble  constit- 

uents of  the  beet. 

Whereas  the  two  first  processes,  particularly  that  of  dialysis, 
are  designed  to  take  place  during  the  treatment,  the  third  is  an 
injurious  side  action  and  should  be  as  much  restricted  as  possible. 
Unfortunately  conditions  most  favorable  for  diffusion  also  aid  in 
the  removal  of  the  relatively  insoluble  substances. 

The  dialysis  of  sugar  from  the  cells  takes  place  more  rapidly, 
the  hotter  and  thinner  the  juice  and  the  finer  the  slices.  It  is 
more  complete  in  proportion  to  the  length  of  process.  Working 
slowly  at  high  temperature,  thin  juice  and  fine  chips  are  also 
the  most  favorable  conditions  for  effecting  solution  of  the  com- 
paratively insoluble  cell-substance. 

It  is  ever  the  business  of  the  sugar-manufacturer  to  consider 
carefully  what  conditions  are  most  favorable  for  greatest  sugar- 
yield.  At  the  same  time  he  must  remember  that  certain  procedure 


38  BEET-SUGAR  MANUFACTURE. 

and  conditions  are  mutually  dependent.  Thus,  for  example,  the 
time  of  diffusion  can  be  shortened  by  working  at  high  temperature 
or  by  stronger  circulation,  but,  on  the  other  hand,  working  at  a 
lower  temperature  is  permissible  if  the  time  of  treatment  is  length- 
ened or  the  slices  are  cut  finer. 

If  it  were  possible  to  carry  out  the  diffusion  process  with  smooth 
chips  of  about  the  size  and  shape  of  linen  thread,  an  almost  ideal 
extraction  would  be  effected,  for  the  whole  action  would  be  com- 
plete in  a  short  time.  In  that  case  only  small  vessels  would  be 
required,  and  there  would  be  much  less  dissolved  from  the  cell- 
walls  and  their  relatively  insoluble  contents,  and,  moreover,  the 
juice  would  be  highly  concentrated. 

Unfortunately  it  is  not  possible  to  prepare  such  chips,  and  if 
such  fine  slices  were  exposed  to  treatment  in  the  diffusers,  they 
would  not  permit  the  passage  of  a  sufficient  current.  Most 
factories  cannot  cut  durable  slices  of  a  thinness  of  2  mm.,  or 
any  kind  of  smooth  slices  of  uniform  cross-section.  The  length 
of  time  required  for  the  diffusion  must  be  regulated  by  the 
time  required  to  extract  the  sugar  from  the  thickest  chips.  The 
greater  the  amount  of  the  latter,  the  longer  the  time  required 
for  the  process  to  obtain  a  good  average  yield  of  sugar,  other 
conditions  being  equal.  The  thinner  chips  are  almost  completely 
exhausted,  and  from  their  cellular  tissue  considerable  non-sugars 
are  dissolved,  while  the  thicker  chips  still  contain  considerably 
more  than  the  average  amount  of  unextrncted  sugar. 

Hacked  or  mushy  chips,  when  extracted  to  the  same  extent, 
give  a  juice  which  is  not  inferior  to  that  obtained  from  firm  and 
uniformly  thick  chips;  at  least,  the  contrary  has  never  been 
proven.  The  inferior  quality  of  juice  which  may  be  obtained 
from  mushy  chips  must,  therefore,  be  alone  attributed  to  an 
uneven  extraction.  To  how  great  an  extent  this  takes  place, 
and  whether  it  is  detectable  in  the  diffuser  juice  or  even  in  the 
purified  juices,  has  never  been  settled.  Since,  however,  bad, 
mushy  chips  can  impede  the  flow  of  all  the  juice,  or  at  certain 
points  whore  masses  of  poorly  extracted  material  occur,  the  aim 
should  always  be  to  prepare  as  good  chips  as  possible. 


EXTRACTION   OF  THE  JUICE.  39 

With  regard  to  the  temperature  cf  the  juice  in  the  battery,  the 
upper  limit  is  determined  by  the  temperature  when  the  chips 
begin  to  soften,  or,  as  it  is  called,  when  they  are  scalded.  Scalded 
chips  lie  so  closely  upon  one  another  in  the  diffusers  and  upon  the 
lower  strainer  that  the  stream  of  juice  runs  extreme!}'  slowly.  This 
temperature  at  which  the  chips  become  soft  varies  with  different 
beets.  In  general,  it  appears  that  freshly  harvested,  ripe  beets 
can  stand  a  higher  temperature  without  injury  than  beets  which 
have  been  stored;  at  all  events,  the  fertilization  and  weather 
which  the  beets  have  experienced  in  their  growth  plays  an  important 
part.  With  sound  beets  the  temperatures  in  the  hottest  calo- 
rizators  can  reach  75°  to  80°  C.  (167°  to  176°  F.)  with  safety,  and 
without  running  any  risk  of  overheating  them.  It  is  worth  men- 
tioning, however,  that  the  temperature  prevailing  in  the  diffusers 
is  always  a  few  degrees  lower  than  that  shown  by  the  thermometer 
in  the  overflow-pipes.  Xo  beet-chips  can  stand  a  temperature  of 
90°  C.  (194°  F.)  without  becoming  soft.  Naturally  a  good  deal 
depends  upon  the  length  of  time  that  the  chips  are  exposed  to  the 
action  of  the  heat,  so  higher  temperatures  can  be  used  when  the 
contents  of  each  diffuser  are  changed  frequently  than  when  the 
work  goes  slower. 

In  working  up  unsound  beets  (i.e.,  those  which  have  been 
frozen  or  are  somewhat  decayed),  the  application  of  high  tem- 
perature is  altogether,  out  of  the  question,  for  the  chips  from  such 
beets,  so  far  as  actual  chips  can  be  made  from  them,  are  originally 
very  soft,  and  become  still  softer  at  a  relatively  low  temperature. 

The  temperature  of  treatment  is  also  different  hi  a  long  battery 
than  in  a  short  one,  and  with  batteries  made  up  of  small  cells  than 
with  large  ones.  The  shorter  the  battery  and  the  smaller  the  indi- 
vidual cells,  the  greater  the  number  of  them  which  can  and  must 
be  maintained  at  the  highest  temperature;  indeed  even  the 
pressure-water  must  be  quite  hot.  The  fundamental  principle 
must  be  to  bring  the  chips  as  quickly  as  possible  to  a  high  tem- 
perature; for  the  cell  becomes  ''killed"  only  at  temperatures 
above  60°  C.  (140°  F.)  and  any  bacterial  action  ceases  at  high 
temperatures.  It  is  possible,  when  the  work  is  carried  out 


40  BEET-SUGAR   MANUFACTURE. 

properly,  to  reach  a  temperature  of  70°  to  75°  C.  (158°  to  167°  F.) 
in  the  second  diffuser,  the  slices  attaining  this  temperature  in 
about  ten  minutes. 

In  order  to  obtain  juice  of  the  highest  concentration,  which 
must  always  be  the  aim,  as  well  as  to  obtain  a  good  extraction, 
the  slices  must  be  surrounded  during  the  whole  process  with 
the  least  possible  amount  of  liquid.  The  concentration  of  the 
diffusion-juice  at  the  same  rate  of  discharge,  and  with  otherwise 
similar  conditions,  will  be  greater  in  proportion  to  the  weight  of 
chips  contained  in  the  diffuser,  or  the  so-called  "feeding- 
capacity."  Ordinarily  this  is  referred  to  every  hectoliter  (26.4 
U.  S.  gallons,  or  22  imperial  gallons)  of  capacity.  In  this  respect 
the  larger  vessels  always  have  a  certain  advantage  over  the 
smaller  ones.  By  "ramming,"  55  to  60  kilograms  (120  to  132 
pounds)  of  chips  can  be  placed  in  each  hectoliter  of  space,  while 
in  the  smaller  diffusers,  particularly  where  the  work  is  carried 
on  rapidly  and  there  is  no  time  for  "ramming,"  frequently  only 
50  kilos  are  placed  in  this  space.  Evidently  the  nature  of  the 
chips  will  play  an  important  part  in  the  filling  of  the  (1  iff  user,  for 
thin  chips  and  those  which  are  from  fresh  beets  will  lie  closer 
together  than  thicker  ones  and  those  from  dried-up  and  withered 
beets. 

From  what  has  been  said,  the  following  typical  methods  of 
working  can  be  distinguished  which,  according  to  the  local  con- 
ditions, have  their  advantages  and  disadvantages: 

1.  Plants  with  the  longer  batteries  of  12  to  14  cells,  of  which 
10  or  12  are  under  pressure,  with  a  small  capacity  of 
20  to  30  hectoliters  (500  to  800  gals.).  The  chips 
must  be  very  fine,  the  temperature  maintained  in  the 
entire  battery  up  to  the  last  cell  must  be  as  high  as 
possible,  using  warm  pressure-water,  and  the  dura- 
tion of  the  diffusion  working  must  be  short,  about 
1  to  1J  hours;  the  change  of  cells  should  he  very 
frequent,  and  the  circulation  rapid.  The  amount 
of  the  diffusion-juice  delivered  will  be  somewhat 
larger  than  usual. 


EXTRACTION   OF   THE   JUICE.  41 

2.  Plants  with  long  batteries  of  12  to  14  cells,  each  with  a 
capacity  of  from  50  to  100  hectoliters  (1300  to  2600 
gals.).  The  chips  must  not  be  too  fine,  but  as  uni- 
form as  possible;  the  temperature  must  be  high  in 
the  first  cells,  but  fall  more  in  the  last  than  in  the 
former  case;  the  pressure-water  should  be  cold  or 
only  lukewarm,  the  time  of  working  should  be  from 
1J  to  If  hours,  the  diffusers  changed  less  frequently 
and  the  rate  at  which  the  diffuser-juice  moves  should 
be  slower  than  in  the  previous  case.  The  amount 
juice  drawn  off  can  be  diminished  to  about  100 >v  of 
the  feeding. 

3.  Work  with  a  short  battery  of  6  to  8  large  cells.  The 
chips  should  be  as  in  Method  2,  the  temperature 
throughout  the  whole  battery  as  high  as  possible, 
the  pressure-water  warm,  the  duration  of  the  diffusion 
shorter  than  under  Method  2  (about  1J  to  1£  hours), 
and  the  diffusers  should  be  changed  even  less  fre- 
quently, the  rate  at  which  the  juice  moves  should  be 
slower,  but  the  amount  of  the  juice  should  be  a  little 
greater. 

If  the  size  of  the  batteries  in  a  given  factory  is  taken  into 
consideration,  it  will  not  be  difficult  to  determine  from  the  above 
three  typical  methods  of  working  how  to  run  the  factory  to 
the  best  advantage,  in  order  to  obtain  juice  as  concentrated  as 
possible  and  a  good  extraction  of  sugar  fromHhe  beets. 

How  far  the  extraction  of  beet-chips  should  be  carried  depends 
on  circumstances.  If  the  battery  is  comparatively  small  and  the 
quantity  of  beets  large,  it  would  not  be  right  to  attempt  to  get 
high  juice-extraction  at  the  expense  of  time  and  labor  for  treating 
the  increased  volume  of  juice;  for  the  gain  in  sugar  would  be  fully 
covered,  if  not  more  than  balanced,  by  the  smaller  daily  output, 
by  the  sugar-loss  of  the  beets  in  storage,  and  the  increase  in  coal 
consumption  made  necessary.  If,  on  the  other  hand,  the  battery 
is  especially  large,  it  would  not  be  good  practice,  when  working 
under  constant  conditions  of  juice-extraction,  to  fail  to  increase 


-{•2  BEET-Sl'GAR   HANUFACTURR 

the  sugar-yield  by  using  the  most  appropriate  temperatures  and 
treatment,  through  fear  of  the  juice  from  the  last  cell  becoming 
impure  enough  to  injure  the  yield. 

While  this  latter  notion  is  widely  prevalent,  it  is  only  worth 
consideration  in  special  cases,  as  when  working  up  decayed  or 
frozen  beets. 

With  sound,  ripe  beets  it  is  true  that  the  undefecated  juice 
from  the  last  cell  often  has  a  very  low  purity,  for  the  water 
dissolves,  according  to  the  nature  of  the  beets,  more  or  less  non- 
sugars,  particularly  the  parapectinates,  in  the  form  of  lime  and 
potash  salts,  but  the  calcium  pectinates  are  precipitated  by  defeca- 
tion and  carbonatation,  and  the  potassium  salts  are  converted 
into  potassium  carbonate.  The  sirup  from  this  purified 
juice  after  proper  neutralization  is  readily  grained  so  that  sugar 
can  be  profitably  made  from  it  with  no  increase  in  cost  of  labor  or 
coal.  The  alkali  carbonates  and  the  alkali  sucrates  which  are 
always  present  to  some  extent  in  the  defecated  and  carbonatated 
after-juices  obviously  must  be  cautiously  neutralized  if  these  juices 
are  worked  up  by  themselves.  When  worked  up  with  the  rest  of 
the  diffusion-juice,  as  customary  in  factories  which  extract  the 
beets  very  thoroughly,  they  do  not  act  injuriously  but  favorably, 
because  the  thin  juice  usually  contains  calcium  salts  which  unite 
with  the  alkaline  carbonates  to  form  a  precipitate  of  calcium 
carbonate.  If  such  soluble  calcium  salts  are  not  present  in  the 
juice  after  it  has  been  defecated,  then  the  carbonates  of  the  alkalies, 
and  especially  the  sucrates,  must  be  changed  to  alkali  sulphites  by 
thorough  saturation  with  sulphurous  acid. 

With  regard  to  the  limit  to  which  the  juice-extraction  may  be 
carried,  it  should  be  noted  that  the  chips,  as  has  already  been 
mentioned,  are  extracted  to  different  extents  in  different  parts  of 
the  diffuser,  and  that  thicker  chips  are  extracted  less,  both  as  to 
the  sugar  and  the  non-sugar,  than  thinner  and  pulpy  ones.  As  to 
the  extraction  in  different  parts  of  the  diffuser,the  results  obtained 
from  experiments  have  not  been  altogether  concordant.  On  the 
whole,  it  can  be  said,  as  might  be  expected,  that  the  amount  of 
sugar  retained  by  the  pulp  is  greater,  the  lower  the  chips  are  in 


EXTRACTION   OF  THE  JUICE.  43 

the  diffuser,  so  that  the  chips  in  the  vicinity  of  the  strainer  con- 
tain at  least  0.1  to  0.2  per  cent,  more  sugar  than  those  at  the  top. 
If  the  strainer  is  conical,  as  the  case  with  diffusers  which  dis- 
charge at  the  bottom,  the  extraction  in  the  middle  of  this  conical 
part  is  likely  to  be  very  deficient  in  case  most  of  the  juice  runs 
through  the  upper  holes  of  the  strainer.  In  large  diffusers  with 
the  cylindrical  part  surmounted  by  a  flat  top,  a  high  sugar- 
content  is  sometimes  shown  by  the  chips  which  remain  in  the 
upper  corners.  All  these  differences  in  the  extent  of  extrac- 
tion are  of  not  much  significance  if  the  chips  are  as  a  whole  very 
thoroughly  exhausted,  but  they  are  worthy  of  more  considera- 
tion when  the  entire  extraction  has  been  so  poor  that  the  chips 
on  an  average  retain  0.5  per  cent,  or  more  sugar.  This  fact 
also  argues  that  the  extraction  should  be  made  as  complete  as 
possible,  because  only  then  does  the  actual  sugar-loss  correspond 
to  that  found  by  research  experiments. 

In  judging  the  extent  of  the  extraction,  it  must  not  be  forgotten 
that  in  the  removal  of  the  spent  chips  the  use  of  considerable 
wash  water  may  cause  a  further  lowering  of  sugar  content,  so 
that  the  sugar  in  the  discharged  chips  is  less  than  that  of  the  chips 
in  the  diffuser.  In  estimating  the  sugar  losses,  the  large  amount 
of  this  waste  water  must  be  taken  into  consideration.  On  the 
other  hand,  when  the  diffuser  is  discharged  by  compressed  air, 
the  sugar-content  of  the  chips  is  invariably  greater. 

Sometimes,  in  spite  of  good  chips  and  correct  procedure, 
an  unusually  high  sugar-content  will  be  found  in  the  extracted 
chips.  In  such  cases,  the  method  of  analysis  should  be  changed, 
either  by  using  a  larger  amount  of  lead  acetate,  or  making  an 
alcoholic  extraction.  If  the  apparent  high  sugar-content  is  not 
explained  in  this  way,  then  a  double  polarization  of  the  alcoholic 
extract  must  be  made. 

The  juice-extraction,  or  the  amount  obtained  from  100  kilo- 
gram* of  the  beets,  is  dependent  on  the  method  of  working.  Before 
increasing  this  amount,  in  case  the  extraction  is  insufficient,  the 
attempt  should  first  be  made  to  improve  the  process  by  heating 
up  the  last  diffuser  to  a  higher  temperature,  or  by  improving 


44  BEET-SUGAR  MANTFAnTKE. 

the  filling  of  the   cells,   while   keeping  the   same   rate   of  juice- 
removal. 

The  measurement  of  the  amount  of  juice  drawn  off  is  usually 
effected  in  an  open  juice-heater.  The  height  of  the  juice  in  the 
tank  is  either  determined  by  an  ordinary  float  or  by  an  automatic 
apparatus  with  a  signal  attachment.  This  measurement,  however, 
must  be  regarded  as  very  inaccurate,  or  at  all  events  insufficient 
for  obtaining  accurate  data.  Sufficiently  accurate  figures  can  be 
obtained  by  measuring  the  juice  in  a  tank  with  an  overflow,  and 
this  tank,  after  each  filling  to  the  overflow-point,  must  be  com- 
pletely emptied.  The  capacity  of  the  tank  is  determined  by 
weighing  the  amount  of  water  which  it  holds.  If  the  overflow  is  so 
arranged  that  it  can  be  easily  raised  or  lowered,  so  that  the  amount 
of  juice  removed  can  be  easily  regulated,  such  a  measuring-tank 
will  fill  all  requirements,  and  the  use  of  automatic  measuring- 
appliances,  of  which  there  are  many  of  satisfactory  construction, 
is  unnecessary. 

Frequently  the  juice  from  each  extraction  is  tested  by  the  spindle, 
and  if  care  is  taken  to  have  a  good  average  sample,  such  a  test  is 
of  great  value.  If,  on  the  other  hand,  it  is  desired  to  regulate 
the  amount  of  juice  drawn  off  according  to  the  density  of  this 
sample,  taking  more  in  case  the  density  is  high,  and  less  if  low, 
this  idea  does  not  seem  to  be  a  good  one.  It  is  superfluous  in  the 
first  place,  because  the  beets  are  already  well  mixed  in  the  slicer, 
and  the  chips  likewise  are  so  well  mixed  that  the  individual  feedings 
of  a  diffuser  during  the  day  cannot  vary  appreciably  in  sugar- 
content.  Consequently  the  density  of  the  juice  will  not  differ 
much  if  the  cells  are  fed  alike.  Furthermore,  the  density  of  the 
juice  and  the  extraction  of  the  chips  depends  upon  so  many  condi- 
tions other  than  on  the  amount  of  juice  drawn  that  any  attempt 
at  regulation  often  causes  more  harm  than  good,  even  if  certain 
cells  actually  do  contain  amounts  of  sugar  different  from  the 
average.  It  is  best,  therefore,  to  change  the  amount  of  juice 
drawn  off,  only  when  the  sugar-content  of  the  exhausted  pulp  is 
abnormal  and  cannot  be  improved  by  other  expedients.  Such  a 


EXTRACTION   OF  THE  JUICE.  45 

regulation  is  only  necessary  after  considerable  intervals  of  time, 
and  the  ordinary  measuring-tanks  give  all  necessary  facilities. 

It  has  been  found  by  experiment  that  concentrated  diffusion- 
juice  usually  is  purer  than  thinner  juice,  and  this  is  particularly 
true  when  the  pressure- water  is  impure.  For  this  reason,  and  also 
in  order  to  economize  in  the  amount  of  coal  used,  the  aim  is  to 
make  the  amount  of  juice  drawn  off  for  a  given  amount  of  beet- 
chips  as  small  as  possible.  Many  factories  only  draw  off  100  liters 
(26.4  U.  S.  gallons)  for  100  kilos  (220  pounds)  of  beets.  More 
than  105  to  110  liters  should  not  be  drawn  if  the  cost  of  coal  is 
high,  and  in  case  the  extraction  is  then  unsatisfactory  it  is  best  to 
improve  the  process  in  other  ways. 

There  is  one  sure  way  of  finding  out  whether  the  adopted 
method  of  working  the  diffusion  is  the  correct  one,  although  requir- 
ing so  much  time  and  labor  that  it  is  seldom  used  in  practice.  The 
method  consists  in  taking  samples  of  juice  from  each  of  the  different 
cells  of  a  battery  at  the  same  time  and  examining  them  for  the 
sugar  and  purity.  From  the  sugar-content,  the  gain  made  in  each 
single  diffuser  is  determined.  If  the  values  thus  obtained  are 
plotted  upon  coordinate  paper  by  taking  the  number  of  the  cell 
as  the  abscissa  and  the  increase  in  per  cent,  of  sugar  in  the  juice  as 
the  ordinate,  a  curve  is  obtained  which,  if  the  method  of  working 
is  correct,  will  have  a  regular  form.  If  the  work  is  being  improp- 
erly conducted,  the  curve  will  be  very  irregular,  showing  that  the 
extraction  in  the  different  diffusers  does  not  take  place  regularly 
and  equally,  and  consequently  the  efficiency  of  the  battery  is  not 
what  it  should  be. 

It  is  not  always  possible  to  judge  the  value  of  juice  from  its 
purity,  because  not  only  is  the  nature  of  the  non-saccharine  material 
very  different,  but  it  is  not  known  which  and  how  much  of  these 
substances  will  be  removed  by  the  subsequent  processes  of  defeca- 
tion and  carbonatation.  It  therefore  sometimes  happens  that  a 
diffusion- juice  of  low  purity  will  yield  better  massecuite  than  a 
purer  juice.  At  the  same  time,  "apparent  purity"  tests  of  diffu- 
sion-juice have  a  certain  practical  value,  as  they  frequently  enable 
conclusions  to  be  drawn  as  to  subsequent  working  and  the  difficul- 


46  BEET-SUGAR  MANUFACTURE. 

ties  likely  to  be  met.  Such  conclusions,  however,  are  only  reliable 
when  many  purit}r  determinations  are  made  systematically;  only 
by  such  tests  is  it  possible  to  judge  whether  a  change  in  the 
conduct  of  the  diffusion  would  be  advantageous,  especially  as  to 
time  and  temperature. 

It  is  quite  wrong  to  judge  the  efficiency  of  the  work  by  com- 
paring the  purity  of  diffused  juice  with  that  of  expressed  juice, 
and  to  conclude  that  the  former  is  better  in  proportion  to  its 
greater  purity.  Further,  it  is  a  well-known  fact  that  the  purity 
of  expressed  juice  varies  with  the  fineness  of  the  pulp  and 
the  amount  of  pressure  applied,  and  that  beets  raised  under 
different  conditions  will  yield  different  amounts  and  qualities 
of  juice  when  pressed.  There  is  no  characteristic  pressed  juice 
which  can  be  taken  as  a  standard,  and  consequently  such  com- 
parisons are  useless. 

Conclusions  as  to  the  efficiency  of  a  factory  method  can  be 
drawn  only  by  comparative  experiments  with  the  diffusers.  Cer- 
tainly it  is  still  doubtful  whether  the  laboratory  test,  which  is  a 
mere  digestion  process,  has  any  practical  worth  as  a  criterion  of 
the  work  on  a  large  scale;  yet  a  juice  obtained  by  digestion  or  in 
similar  manner,  if  made  from  the  same  pulp,  is  certainly  to  be 
preferred  to  expressed  juice  for  comparing  with  diffusion-juice. 

The  best  way  to  judge  of  the  effectiveness  of  a  diffusion  process 
is  to  make  comparative  experiments  with  two  batteries  working 
the  same  beet  material.  Inasmuch  as  it  is  difficult  and  expensive 
to  arrange  for  such  experiments,  as  a  rule  the  actual  results  of 
parallel  researches  made  with  small  experimental  batteries  must 
be  depended  upon  to  regulate  factory  control.  In  general,  the  vital 
points  to  be  kept  in  mind  are  to  maintain  good  extraction  and  con- 
centrated juice,  using  systemized  method  and  regularity  in 
running. 

The  changes  which  the  constituents  of  the  beets  undergo  in 
any  special  diffusion  process  are  but  little  understood.  The  chief 
constituent,  the  sugar,  speaking  generally,  suffers  no  perceptible 
change  even  if  the  diffusion  is  slow  and  at  high  temperature,  for 
many  experiments  show  no  increase  in  the  amount  of  invert-sugar, 


EXTKACTIOX    OF   THE  JUICE.  47 

or  at  least  only  a  doubtful  one,  and  doubtful  in  so  far  as  it  is  uncer- 
tain whether  slight  increases  in  the  amount  of  invert-sugar  actually 
occur  from  the  sugar  in  the  battery  or  whether  substances  with  a 
reducing  action  are  not  formed  from  other  constituents.  The 
amount  of  reducing  substances  in  the  diffuser- juice  amounts  in 
general  to  from  0.05  to  0.15  per  cent.,  according  to  the  amount 
present  in  the  beets.  Of  the  albuminoids,  a  greater  amount  appears 
to  remain  in  the  beet-pulp  the  hotter  the  diffusion .  The  amount 
of  acid  present  in  the  juice  varies  but  slightly.  Its  acid  reaction 
is  partly  due  to  free  acid  and  partly  to  acid  potassium  salts  which 
were  either  or'ginally  present  in  the  beets  or  were  formed  during 
the  diffusion.  The  amount  of  pec  tic  substances  which  go  into 
solution,  and  of  difficultly  soluble  potassium  and  calcium  salts, 
increases  with  the  duration  of  the  time  of  working  and  with  the 
number  of  cells  in  a  battery.  The  method  of  cultivating  the  beets 
and  their  ripeness  also  has  an  important  influence  upon  the  solu- 
bility of  all  these  substances.  Beets  which  have  been  unneces- 
sarily strongly  fertilized  with  potash  and  nitrogen  will  always 
yield  larger  amounts  of  this  non-saccharine  material  than  beets 
which  have  been  normally  fertilized  or  with  sufficient  amounts  of 
phosphoric  acid;  not  only  as  this  non-saccharine  material  is  pres- 
ent in  greater  quantities  and  in  a  more  soluble  condition  in  the 
former,  but  because  such  beets  are  always  more  difficult  to  ex- 
tract sugar  from,  so  that  it  is  necessary  to  make  use  of  higher  tem- 
peratures and  expose  them  to  a  longer  diffusion.  The  constitu- 
ents of  frozen  or  decayed  beets  undergo  greater  changes  during 
the  diffusion,  particularly  when  they  are  worked  up  hot  and  slowly; 
the  amounts  of  in  vert -sugar  and  acid  as  well  as  of  pec  tic  substance 
being  notably  increased. 

Recently,  particular  attention  has  been  paid  to  the  action  of 
micro-organisms  and  ferments  upon  the  juices,  especially  during 
diffusion.  Ferments  have  been  found  in  the  beets  themselves — 
namely,  invertin  and  a  zymase.  Micro-organisms,  on  the  con- 
trary, are  not  present  in  healthy  beets;  they  and  their  germs 
get  into  the  diffusion  with  the  dirt  and  dirty  water,  as  well  as  in 
the  factory  supply.  Their  number  depends  entirely  upon  the 


48  BEET-SUGAR  MANUFACTURE. 

condicrons  prevailing  in  individual  factories.  Dirty  beets,  and 
those  washed  with  impure  water,  naturally  introduce  more  of 
such  forms  of  life  into  the  diffusion  than  do  beets  which  have 
been  well  washed  and  rinsed  with  pure  water.  Good  spring 
water  and  river  water  containing  but  few  germs.  Polluted 
water,  or  the  purified  water  which  some  factories  are  compelled 
to  use,  contain  a  great  many  of  them.  Consequently,  the  number 
of  micro-organisms  and  germs  in  the  juice  of  the  first  and  last 
diffuser  may  rise  to  many  thousand  per  cubic  centimeter. 

Among  these  micro-organisms,  however,  many  are  found 
which  have  no  action  upon  sugar.  Those  that  act  upon  the 
sugar  are  chiefly  Leuconostoc,  Bacterium  coli,  Bacillus  mesen- 
tericus,  and  subtilis,  and  related  species. 

If  the  forms  of  life  present  decompose  sugar,  it  is  evident 
that  corresponding  decomposition  products  must  appear,  since 
almost  every  individual  kind  of  .micro-organism  produces  a  char- 
acteristic product.  As  a  rule,  the  sugar  solution  becomes  acid, 
but  sometimes  it  turns  alkaline.  Invert-sugar  is  formed  in  many 
cases;  at  other  times  it  is  either  not  formed  at  all,  or  is  decom- 
posed as  fast  as  it  is  formed.  Not  a  few  bacteria  produce  slimy 
or  gummy  substances,  others  alcohol  and  various  gases  such  as 
carbon  dioxide,  methane,  hydrogen,  etc.  The  presence  of  micro- 
organisms is  often  recognized  by  the  appearance  of  such  gases, 
even  when  the  amount  of  sugar  decomposed  is  small.  In  other 
cases  it  is  more  difficult  to  detect  the  action  of  bacteria,  as  the 
qualitative  detection  of  the  decomposition  products  is  in  many 
cases  difficult  and  the  quantitative  estimation  altogether  impos- 
sible. There  is  no  question,  therefore,  but  that  when  the  condi- 
tions are  favorable  to  bacterial  action,  large  amounts  of  sugar 
may  be  decomposed  without  superficial  examination  showing  any 
indication  of  such  decomposition. 

The  most  essential  conditions  favoring  the  activity  of  micro- 
organisms are,  however,  favorable  temperature  and  sufficient 
time.  Such  conditions  are  never  met  with  in  a  modern,  carefully- 
conducted  sugar-factory.  Only  very  few  bacteria  are  active  at 
temperatures  as  high  as  60°  to  70°  C.,  and  these  lose  their 


EXTRACTION   OF  THE  JUICE.  49 

activity,  or  die,  if  the  temperature  is  raised  to  75°  to  80°.  The 
ferments,  to  be  sure,  still  act  at  this  high  temperature,  but  the 
amount  of  ferments  present  in  the  beets  themselves  is  very 
small  and  ferments  are  formed  from  micro-organisms  only  when 
the  latter  are  active. 

In  the  diffusion  process  the  temperature  in  the  diffusers  is 
never  below  55°  to  60°  C.,  except  in  the  first  and  last  diffusers 
and  rarely  in  the  diffuser  next  to  the  last;  all  other  diffusers 
have  a  temperature  of  at  least  70°  C.,  and  most  of  them  are 
between  75°  and  80°  C.  The  chips  and  juice,  therefore,  are  at 
temperatures  favorable  to  the  development  of  bacteria  only  for 
about  ten  minutes  at  the  start  and  for  from  ten  to  twenty 
minutes  at  the  end  of  the  diffusion  process.  In  this  short  time 
it  is  not  possible  for  bacteria  to  form  ferments  or  decompose 
appreciable  amounts  of  sugar,  especially  as  it  requires  some 
time  for  bacteria  to  become  accustomed  to  new  environment. 
Although  it  is  sometimes  asserted  that  sugar  is  decomposed 
during  the  passage  of  the  chips  from  the  slicing-machine  to  the 
diffusers,  this  has  been  disproved  by  many  experiments.  Cosettes 
from  healthy  beets  will  keep  for  several  hours  at  ordinary  tem- 
peratures without  suffering  any  sugar  loss. 

If  the  diffusion  and  subsequent  treatment  is  carried  out 
properly — at  high  temperatures  and  with  rapid  movement  of  the 
juice — it  is  impossible  for  appreciable  amounts  of  sugar  to  be 
decomposed. 

The  undoubted  possibility  that,  in  exceptional  cases  when 
proper  conditions  are  not  maintained,  the  action  of  bacteria  may 
become  marked  should  tend  to  make  the  manufacturer  exercise 
all  the  more  care  in  maintaining  proper  care.  The  use  of  pre- 
servatives, such  as  carbolic  acid,  acid  sulphites,  formalin,  etc., 
is  quite  unnecessary,  aside  from  the  fact  that  the  action  of  these 
preservatives  is  doubtful  and  they  are  expensive.  Formalin, 
besides  preventing  fermentation,  is  said  to  have  a  favorable 
action  as  a  precipitant  of  protein  and  peptic  substances,  but  in 
order  to  obtain  such  action,  the  amount  required  makes  it  too 
expensive  to  be  profitable.  When  bisulphites  are  used,  of  which 


50  BEET-SUGAR  MANUFACTURE. 

as  a  rule  one  liter  of  a  30°  Be.  solution  is  added  to  100  kg.  of 
beets,  hydrogen  sulphide  is  frequently  formed. 

For  practical  purposes,  the  question  as  to  the  injurious  effect  of 
micro-organisms  upon  diffusion  can  be  regarded  as  wholly  an- 
swered, inasmuch  as  many  experiments  have  shown  that  there 
is  no  perceptible  sugar  loss  under  normal  conditions.  All  the 
sugar  originally  present  in  the  beet,  within  the  limits  of  error 
arising  from  sampling  and  methods  of  analysis,  can  be  accounted 
for  by  that  found  in  the  diffusion-juice  and  in  the  waste 
products. 

Many  changes  in  the  ordinary  methods  of  conducting  diffusion 
have  been  tried,  without  proving  of  much  importance  or  finding 
permanent  application  in  the  industry. 

The  attempts  to  carry  out  a  continuous  diffusion  in  one  cell 
deserve  particular  attention.  The  idea  is  certainly  as  old  as  the 
diffusion  process  itself,  although  up  to  the  present  time  those 
arrangements  which  have  been  tried  in  practice  have  yielded  a 
thin  juice,  and  the  extraction  of  the  sugar  from  the  beets  has  been 
incomplete  and  uneven.  Most  plans  for  this  diffusion  method 
exist  only  on  paper.  If  it  were  possible  to  overcome  the  above- 
mentioned  evils,  the  continuous  diffuser  would  without  doubt 
replace  those  now  in  use.  A  diffusion  which  is  to  take  place  con- 
tinuously must  be  so  arranged  that  the  juice  in  a  constant  and 
steady  stream  meets  the  beet-chips  moving  in  the  opposite 
direction.  Consequently,  all  disturbances  caused  by  the  strainers 
at  the  bottom  of  the  ordinary  cells,  and  the  sugar-loss  caused 
by  the  amount  wasted  in  the  water  while  emptying  cells,  will 
be  avoided. 

Other  experiments  have  been  tried  of  running  the  current  of 
juice  from  the  bottom  to  the  top  of  the  cell,  with  the  idea  of 
floating  the  chips  and  thereby  preventing  the  stoppage  of  the 
holes  in  the  strainer  at  the  bottom.  But  the  chips  which  are 
floated  upward  by  the  stream  tend  to  stop  up  the  holes  in  the 
strainer,  which  must  then  be  placed  in  the  top  of  the  diffuser 
and  cause  about  as  much  trouble.  Furthermore,  circulation 
from  top  to  bottom  is  better  because  the  denser  juice  does 


EXTRACTION  OF  THE  JUICE.  51 

not  become  mixed  so  much  with  the  thinner  juice  which  fol- 
lows it. 

In  order  to  coagulate  the  protein  matter  in  the  cells  of  the 
beet-chips  at  the  start,  so  that  it  cannot  pass  through  the  cell- 
walls,  the  chips,  as  soon  as  put  in  the  diffuser,  have  been  sub- 
jected to  the  action  of  steam  or  hot  juice.  It  has  even  been 
proposed  to  construct  the  beet-slicing  machine  so  that  the  beets 
will  be  sliced  under  a  layer  of  hot  diffuser-juice,  so  that  the 
slices  do  not  come  in  contact  at  all  with  air  but  are  flushed  by 
the  juice  directly  into  the  diffusers.  At  all  events,  the  advan- 
tage is  gained  that  the  beets  are  more  easily  sliced  under  the 
hot  juice.  But  it  is  doubtful  whether  such  a  process  can  prove 
successful.  During  the  short  time  that  the  chips  are  exposed 
to  the  air  under  ordinary  conditions,  there  is  no  decomposition, 
so  that  the  coagulable  proteins  do  no  harm  to  the  juice. 
As  a  matter  of  fact,  however,  no  appreciably  greater  quantity 
of  protein  passes  into  the  juice  when  the  slices  are  heate  I 
in  the  usual  manner  than  when  they  are  suddenly  heated  to 
above  70°  C. 

There  is  just  as  little  advantage  to  be  gained  by  heating  the 
chips  to  100°  C.  (212°  F.)  with  steam  or  juice  in  a  freshly  filled 
diffuser. 

The  process  is  not  advisable,  moreover,  because  of  the  danger 
of  sometimes  scalding  the  chips  in  places  and  so  hindering  circu- 
lation. This  can  be  obviated  by  treating  fresh  chips  with  liquor 
at  75°-80°  C.  from  the  previous  diffuser,  by  pumping  the  juice 
through  the  chips  and  heater  several  times.  The  advantage  of 
this  method  of  working  lies  more  in  the  fact  that  the  fresh  chips  are 
at  once  subject  to  diffusion  with  hot  juice.  The  extraction  of  the 
sugar  from  the  chips  also  takes  place  more  rapidly,  fewer  cells  are 
required  in  the  battery,  and  the  juice  is  drawn  off  more  con- 
centrated. The  process  is  also  simplified  so  far  as  only  the 
freshly  filled  cell  needs  heating,  the  other  calorizators  being 
unnecessary,  particularly  when  hot  pressure-water  is  used.  The 
handling  of  the  battery  will  be  more  complicated,  however, 
inasmuch  as  each  diffuser  will  require  a  special  system  of 


52  BEET-SUGAR  MANUFACTURE. 

valves  and  conducting  pipes  to  run  the  juice  back  and 
forth. 

With  regard  to  the  fact  that  the  air  contained  in  the  chips 
proves  a  hindrance  for  the  quick  extraction  of  the  sugar,  the 
proposal  has  been  made  to  remove  the  air  from  the  freshly  filled 
diffuser  by  means  of  a  pump  before  mashing  the  chips  with  juice. 
The  advantage  gained  by  this  method  of  operating  is  so  slight 
that  it  is  not  to  be  recommended  on  account  of  the  increased 
expense  of  installation  and  operating. 

In  order  to  enrich  the  wash-water  from  the  filter-presses, 
which  cannot  be  utilized  in  the  dry  clarification  process,  experi- 
ments in  sending  it  back  always  to  that  cell  in  the  diffusion, 
which  holds  juice  of  approximately  the  same  concentration,  have 
been  tried  with  success.  This  method  does  not  increase  the 
amount  of  juice  drawn  off  to  the  extent  the  wash-water  has  been 
added,  since  the  juice  is  notably  more  concentrated.  In  general, 
however,  it  is  hardly  worth  while  to  send  this  water  back  to  the 
diffuser,  because  the  work  then  requires  much  more  attention, 
more  control,  and  a  new  system  of  piping  is  necessary,  and  finally 
the  advantage  to  be  gained  is  not  very  great;  with  a  continuous 
diffuser,  on  the  other  hand,  such  waste-waters,  like  the  diffusion 
waste-waters  also,  could  be  utilized  very  advantageously. 

Diffusion  troubles  sometimes  make  a  different  procedure 
necessary.  Such  irregularities  may  be  caused  either  by  the  kind 
of  beets,  the  inattention  of  workmen,  or  by  a  factory  shut-down. 

One  of  the  most  difficult  tasks  is  to  handle  frozen  or  decayed 
beets  successfully,  or  such  as  cause  evolution  of  gases  in  the 
diffusion,  without  making  the  process  too  long,  or  getting  poor 
extraction  and  impure  juice. 

Beets  which  have  been  thoroughly  frozen  by  a  strong  and 
extended  frost  are  not  thawed  by  the  warm  water  in  the  carrier 
and  washing-machines.  It  is  lucky  if  they  are  thawed  enough 
to  be  washed  clean  of  adhering  dirt.  In  the  beet-slicers  it  is 
impossible  to  obtain  good  chips  from  such  beets;  the  ordinary 
knives  are  useless  as  a  rule,  so  that  "  finger-knives "  must  be 
employed,  and  preferably  those  of  roof  ridge  shape.  Short  chips 


EXTRACTION   OF  THE  JUICE.  53 

are  obtained  mixed  with  a  quantity  of  mush,  which  makes 
satisfactory  diffusion  work  very  difficult.  Frequently  the  chips, 
owing  to  the  ice  which  they  contain,  when  mashed  with  warm 
juice  freeze  together  in  solid  lumps  and  do  not  thaw  during  the 
whole  diffusion,  or  at  least  only  partly.  When  the  cells  are 
emptied,  there  will  be  mixed  with  the  normally  extracted  chips 
those  from  these  frozen  lumps,  which  will  be  little,  if  any, 
extracted.  In  order  to  avoid  this  trouble  as  much  as  possible, 
it  is  advisable,  as  the  frozen  slices  are  going  into  the  cell,  to 
run  juice,  as  hot  as  practicable,  in  at  the  bottom.  For  the 
rest,  it  is  necessary  to  work  the  other  diffusers  at  as  low  a 
temperature  as  possible,  because  the  cell-walls  of  the  beet  have 
been  partially  destroyed  by  the  frost,  and  the  chips  conse- 
quently are  apt  to  become  too  soft.  Decayed  or  badly  preserved 
beets  must  be  also  worked  up  at  low  temperatures.  Conse- 
quently, to  avoid  undesirable  pressure  in  the  diffusers,  the 
working  temperature  is  lowered  in  proportion  to  the  number 
of  decayed  or  frozen  beets. 

Under  such  circumstances,  no  matter  how  the  work  is  done, 
it  is  self-evident  that  the  chips  will  be  very  unevenly  exhausted. 
Of  two  evils  it  is  necessary  to  choose  the  lesser,  and  in  this  case 
the  lesser  evil  is  the  high  sugar-loss,  compared  with  the  use  of 
high  temperatures,  which  effect  complete  stoppage  of  the  circu- 
lation and  hence  make  it  absolutely  impossible  to  continue  the 
process.  The  high  sugar-loss  is  likewise  a  lesser  evil  than 
extracting  a  very  impure  juice,  which  will  always  come  from 
working  slowly  at  high  temperatures  with  such  beets. 

The  evolution  of  gases  in  diffusion  causes  less  trouble  than 
formerly,  on  account  of  the  process  being  now  conducted  hotter 
and  more  rapidly.  This  phenomenon  is  caused  by  fermentation 
brought  about  by  action  of  bacteria,  and  is  made  evident  by  a 
strong  frothing  in  the  last  diffusers.  The  cause  of  this  frothing  is 
that  certain  gases,  particularly  hydrogen  and  carbonic  acid,  are 
set  free  by  the  fermentation.  It  is  not  yet  perfectly  clear  what 
kind  of  micro-organisms  cause  the  fermentation;  apparently 
they  are  anaerobic,  as  their  activity  is  noticeable  only  within 


54  BEET-SUGAR  MANUFACTURE. 

the  diffuser  and  ceases  at  once  when  the  diffuser  is  emptied 
and  its  contents  exposed  to  the  air.  The  bacteria  probably 
come  from  the  soil,  for  the  evolution  of  gases  frequently  occurs 
in  working  with  very  dirty  beets.  The  best  means  of  protection, 
therefore,  lies  in  carefully  washing  the  beets,  and  using  pure 
pressure-water.  High  temperatures  do  not  seem  to  kill  these 
bacteria,  for  they  are  exposed  to  80°-85°  C.  in  the  first  diffusers. 
Their  "  temperature-optimum "  lies  between  40°  and  50°  C. 

If  in  a  battery  the  gas-evolution  has  taken  place  to  the  extent 
that  the  rate  of  flow  of  the  juice  is  considerably  diminished,  the 
best  way  to  remedy  this  is  to  draw  off  the  juice  immediately. 
It  is  ineffective,  or  partially  so,  simply  to  remove  the  gas  by 
blowing  it  off  through  the  air-valves,  because  the  gas  collects 
only  partly  in  the  top  of  the  diffuser,  while  the  greater  part  of 
it  remains  as  a  froth  between  the  chips  at  the  places  where  it 
is  formed.  The  whole  contents  of  the  last  diffusers  are,  there- 
fore, foamy,  and  the  current  of  juice  is  greatly  impeded.  The 
slower  the  circulation  and  the  longer  the  time  taken  up  by  the 
diffusion  working,  the  more  gas  will  be  generated,  so  that  as  a 
result,  eventually  the  flow  of  the  juice  will  stop  entirely.  If, 
however,  the  juice  is  at  once  removed  and  the  diffusers  are  well 
washed  out,  usually  this  unpleasant  occurrence  will  not  take 
place  again  if  the  work  is  started  hot  and  quick,  and,  with  a  shorter 
battery,  avoiding  interruption  of  the  circulation.  The  increased 
loss  in  sugar  owing  to  the  amount  remaining  in  the  pulp,  from 
this  method  of  working,  will  in  many  cases  be  compensated  by 
saving  of  time  consumed  in  the  operation  and  by  the  extraction 
of  purer  juice,  since  extraction  in  a  foamy  diffuser,  even  with 
slow  working,  is  usually  unsatisfactory.  Incidentally  it  should 
be  noted  that  there  is  danger  from  explosions,  which  can  be 
readily  caused  by  opening  the  diffuser  in  the  presence  of  a  naked 
light,  and  particularly  there  should  be  special  caution  in  opening 
the  lower  manholes,  as  usually  there  is  a  strong  pressure  within 
the  diffuser. 

A  phenomenon  very  similar  to  the  gas  evolution  which  was 
described  above  is  sometimes  observed  if  the  beets  contain  large 


EXTRACTION   OF    THE  JUICE.  55 

amounts  of  enclosed  air  which  cannot  immediately  escape  during 
the  mashing  of  a  freshly  filled  diffuser.  These  gases,  however, 
contain  carbonic  acid  and  are  not  formed  during  the  diffusion, 
but  are  already  contained  in  the  beets,  and  on  account  of  their 
small  amount  cannot  cause  much  disturbance  in  the  process.  It 
is  sufficient  to  remove  them  from  time  to  time  by  means  of  air- 
cocks  or  vacuum  apparatus  on  the  diffusers. 

The  diffusion  can  also  be  impeded  greatly  by  bad  slices  made 
from  beets  that  have  gone  to  seed.  Such  beets,  particularly 
when  they  have  old  seed-stalks,  possess  a  very  woody  tissue 
which  dulls  the  knives  in  the  slicer  or  covers  them  with  fibres. 
If  the  farmer  cannot  be  made  to  throw  out  all  such  beets  when 
harvesting,  there  is  no  other  help  except  changing  the  knives 
frequently  and  using  either  Konigsfelder  or  "finger"  knives  with 
notched  guards.  Ordinarily  such  beets  are  met  with  only  at 
the  beginning  of  the  campaign,  when  the  early  beets  are  delivered 
at  the  factory.  The  causes  of  the  appearance  of  seed-beets  are 
usually  a  long-continued  period  of  growth,  heavy  and  unequal 
fertilization,  interrupted  growth  by  night  frosts,  etc.,  to  which 
the  early  beets  are  more  subject  than  those  which  are  sowed  later. 

Unpleasant  interruptions  and  troubles  in  diffusion  are  often 
caused  by  lengthy  stoppages  in  other  parts  of  the  factory.  If 
this  be  due  to  a  limited  supply  of  chips  (from  troubles  in  the 
wash-house  or  in  the  beet-slicers) ,  it  is  well  to  remove  a  measuring- 
tankful  of  juice  every  half-hour,  and  in  this  way  cut  out  the  last 
cell  of  the  battery,  in  order  that  the  juice  move  more  slowly 
without  dissolving  out  too  much  of  non-saccharine  material. 
This  is  not  applicable  when  the  trouble  is  at  some  later  stage  of 
the  process,  and  in  this  case  deterioration  of  the  juice  is  the 
inevitable  consequence. 

This  deterioration  causes  most  trouble  when  the  delay  in 
process  comes  from  slow-running  filter-presses,  because  one  of 
the  principal  causes  of  slow  filtration,  particularly  in  working  up 
beets  which  are  unripe  and  have  been  strongly  fertilized  with 
nitrogen,  is  due  to  the  presence  of  pectin  or  similar  substances, 
separating  as  a  slimy  mass  in  defecation.  The  amount  of  these 


56  BEET-SUGAR  MANUFACTURE. 

substances  increases  with  the  slow  working  of  the  diffusion.  In 
such  cases  it  is  best  to  lower  the  temperature  in  the  diffusion  as 
much  as  is  consistent  with  a  satisfactory  exhaustion  of  the  beets, 
and,  if  possible,  the  hottest  cells  should  be  at  a  temperature  of 
from  68°  to  70°  (155°  to  158°  F.).  This  usually  extracts  juice 
which  will  run  better  through  the  presses,  and  the  work  goes 
more  quickly. 

If  the  disturbance  in  the  factory  is  more  than  temporary,  the 
battery  should  be  at  once  "  sweetened  off/'  so  that,  when  the 
difficulty  has  been  removed,  the  work  can  start  fresh.  With 
sound  and  good  beets,  however,  a  stoppage  of  twelve  hours  in 
the  battery  ought  not  to  do  much  harm,  if  the  temperature  is 
lowered.  Many  factories  consequently  do  not  " sweeten  off"  the 
battery  over  Sunday,  but,  after  drawing  off  the  thicker  juice, 
allow  it  to  stand,  in  order  to  begin  the  evening  work  with  the 
thinner  juice.  This  practice,  however,  is  not  to  be  recommended, 
for  the  juice  always  deteriorates  considerably.  There  is  also  no 
advantage,  since  the  only  reason  for  allowing  juice  to  stand  in  the 
diffuser  is  to  economize  coal,  and  this  is  unnecessary,  because 
the  exhaust-steam  is  not  needed  for  evaporation,  and  unless 
used  will  be  wasted. 

Inattention  and  carelessness  on  the  part  of  workmen  in 
charge  of  a  battery  will  often  cause  much  trouble.  If  the 
prescribed  temperatures  are  not  maintained,  if  bad  chips  enter 
the  diffuser,  or  an  insufficient  amount  of  juice  is  drawn  off,  the 
result  will  be  poor  pressures  in  the  battery,  or  a  poor  extraction. 
If  excessive  temperature  in  the  battery  is  detected  soon  enough, 
it  is  advantageous  to  let  cold  water  into  the  overheated  diff users 
and  to  push  on  as  quickly  as  possible,  so. that  the  hot  liquid  is 
allowed  to  act  upon  the  chips  but  a  short  time.  If  the  circula-* 
tion  has  already  become  retarded  on  account  of  the  high  tem- 
perature, the  frequently  employed  method  of  shortening  the 
battery  helps  only  when  it  is  known  that  the  cell  causing  the 
trouble  is  near  the  last  in  the  series;  otherwise  the  damage  is 
merely  augumented  by  increasing  the  sugar-loss  in  the  extracted 
residues. 


KXTKAC TIOX   OF   THE   JUICE.  57 

If  poor  pressure  in  the  diffusion  battery  is  caused  by  beet- 
chips,  which  have  been  softened  by  too  high  temperature  packing 
against  the  strainer  and  stopping  up  its  holes,  the  difficulty  can 
be  overcome  by  reversing  the  flow  for  a  short  time.  To  do  this, 
close  the  water-valve  on  the  last  cell  and  open  the  uptake-valve 
of  the  cell  which  is  next  to  the  one  which  has  just  been  emptied. 
At  the  same  time  the  water-valve  on  the  freshly  mashed  cell  is 
opened  and  the  water  now  forces  the  j  uice  in  all  the  cells  up 
through  the  strainer,  so  that  the  holes  of  the  latter  are  freed 
from  the  clogging  beet-chips.  If,  after  a  short  time,  the  flow  is 
turned  in  the  original  direction,  the  chips  are  no  longer  packed 
against  the  holes,  and  the  pressure  in  the  diffusion  battery  will 
be  very  much  improved. 

Leaky  valves  are  often  the  cause  of  irregular  working  in 
diffusion.  If  a  water-valve  does  not  close  tightly,  water  con- 
tinually enters  the  diffuser,  together  with  the  juice,  causing  a 
constant  dilution  and  an  unsatisfactory  sugar-extraction.  If  a 
juice-valve  is  not  tight,  the  juice  will  likewise  become  thinner 
when  it  leaves  the  battery.  The  batteryman,  therefore,  must 
make  sure  that  all  the  valves  are  tightly  closed  after  each  cell 
has  been  emptied,  and  that  neither  water  nor  juice  escapes  from 
the  upper  pipe  discharging  into  the  diffuser. 

With  good  valve-washers  of  rubber  or  vulcanized  fibre,  and 
with  the  disc  properly  attached  to  the  stem,  there  is  seldom  any 
trouble  from  leakage. 

Invariably  a  constant  chemical  control  of  the  diffusion,  night 
and  day,  is  absolutely  essential.  The  mere  fact  that  workmen 
know  that  every  mistake  will  be  detected  stimulates  them  to 
irivater  care  in  running  the  battery. 

Particular  attention  must  be  paid  to  starting  and  sweetening 
off  the  battery.  In  order  to  start  a  battery,  three  cells  are  filled 
with  hot  water  by  allowing  the  water  to  flow  from  one  vessel  to 
another  and  warming  it  in  the  calorizators,  or  the  hot  water  is 
taken  from  another  part  of  the  factory  (condenser-water,  exhaust- 
steam,  etc.).  The  temperature  of  this  water  should  in  general 
not  exceed  70°  C.  (158°  F.),  otherwise  the  fresh  chips  are  likely 


58  BEET-SUGAR   MANUFACTURE. 

to  be  scalded  at  the  start,  and  consequent!}*  cause  poor  pressure. 
Frequently  the  beet-slicers  are  made  a  little  thicker  than  usual 
at  the  beginning  of  the  work  in  order  to  avoid  bad  pressure 
at  this  time.  One  after  another,  four  or  five  diff users  are 
filled  with  the  hot  water,  of  course  taking  precaution  to  bring 
the  juice  to  the  right  temperature  as  it  passes  from  one  cell  to 
another.  Then  the  first  juice  is  run  off  into  the  measuring- tank, 
and  usually  half  a  tankful  is  drawn  from  each  of  the  first  two 
cells.  When  in  this  way  the  usual  number  of  diff  users  have  been 
filled  with  chips  and  put  in  operation,  the  battery  is  ready  to  run 
in  the  ordinary  manner,  the  prescribed  temperatures  being  main- 
tained and  the  last  cells  systematically  cut  out  and  emptied  one 
after  the  other.  Naturally  the  extracted  pulp  from  the  first  dif- 
fusers  is  always  very  thoroughly  exhausted,  and  usually  retains 
but  traces  of  sugar.  The  juice  which  is  at  first  extracted  is  quite 
thin,  and  only  becomes  of  normal  density  after  six  or  seven  cells 
are  drawn. 

The  stopping  or  "  sweetening  off  "  of  a  battery  is  carried  out 
in  such  a  way  that  one  vessel  after  another  is  shut  out  of  the 
series  after  two  measuring- tankfuls  of  juice  have  at  intervals  been 
withdrawn  from  each.  Finally,  four  cells  are  left  connected  with 
one  another,  and  juice  is  drawn  away  until  the  last  juice  con- 
tains only  0.3  to  0.5  per  cent,  of  sugar.  With  poor  beets  it  is  best 
to  put  this  limit  higher,  and  to  stop  when  the  juice  contains  from 
0.5  to  0.75  per  cent,  of  sugar.  Then  the  chips,  even  in  the  last 
diffuser,  are  sufficiently  extracted;  and  if  the  amount  of  sugar 
which  they  retain  is  somewhat  greater  than  is  the  case  in  the 
normal  working  of  the  battery,  still  this  small  loss  does  not  come 
into  consideration  in  comparison  with  the  lowering  of  the  purity 
of  the  juice.  The  last  juice  taken  from  the  diffuser  has  a  varying 
composition,  depending  upon  the  character  of  the  other  juice.  Its 
purity  is  greatly  diminished,  and  even  after  defecation  is  still 
very  impure;  it  contains  in  particular  many  organic  non- 
saccharine  substances,  which  in  the  process  of  defecation  form 
calcium  salts  to  some  extent,  and  render  the  further  working-up 
of  the  juice  more  difficult,  especially  the  boiling  of  the  last  week's 
after-products. 


EXTRACTION"    OF   THE   JUICE.  .")!> 

The  exhausted  chips  are  discharged  through  a  manhole  which 
is  either  at  the  side  or  the  bottom  of  the  diffuser.  In  order  that  the 
emptying  may  take  place  rapidly  and  thoroughly,  it  is  necessary  to 
observe  certain  precautions.  First  of  all,  by  opening  the  upper  air- 
cock  the  pressure  within  the  cell  is  diminished;  after  this  the 
lid  to  the  lower  manhole  can  be  cautiously  unscrewed.  When  the 
sputtering  has  ceased,  the  lower  manhole  should  then  be  quickly 
opened,  and  immediately  afterwards  the  cover  of  the  upper  man- 
hole should  be  raised.  The  contents  of  the  diffuser  will  then  fall 
out  in  a  steady  stream  into  a  hydraulic  carrier,  which  must  be  wide 
and  deep  enough  to  take  up  the  mass  of  exhausted  pulp.  Diff users 
which  are  provided  with  discharge-doors  at  the  bottom  are  emptied 
very  completely  in  this  way,  so  that  it  is  only  necessary  afterwards 
to  rinse  them  out  with  a  little  wTater.  In  the  case  of  cells  with 
discharging-doors  at  the  side,  more  or  less  of  the  chips  will  remain 
lying  in  the  corner  opposite  to  the  manhole,  but  the  amount  of 
exhausted  pulp  finally  left  in  the  cell  is  diminished  by  flushing  out 
with  water  from  above,  or,  still  better,  by  letting  in  the  water 
beneath  the  strainer.  When  the  latter  method  is  employed  care 
must  be  taken  to  see  that  the  strainer  is  firmly  fastened  in  position 
so  that  it  is  not  displaced  in  the  operation. 

The  hydraulic  carrier  has  now  come  into  almost  universal  use 
for  carrying  away  exhausted  chips.  It  is  the  simplest  of  all  meth- 
ods for  transporting  them  in  a  horizontal  direction.  All  the  rules 
which  were  laid  down  with  regard  to  the  beet-carrier  will  hold  here 
also,  particularly  with  regard  to  the  necessity  of  avoiding  any 
damming  up  at  the  elevator.  As  the  carriers  always  have  con- 
siderable width  and  breadth,  it  is  not  necessary  to  provide  much 
of  a  fall;  one  of  about  50  mm.  (2  inches)  suffices.  For  the  rest, 
the  dimensions  of  the  carrier  are  governed  solely  by  the  capacity 
of  the  diffuser;  it  is  made  deeper  and  broader  in  proportion  as  the 
cell  is  large,  so  that  there  will  be  room  enough  when  the  chips  are 
suddenly  dropped  into  the  carrier. 

Although  the  chips  are  shot  out  of  the  cells  with  a  large  amount 
of  water,  which  amounts  to  more  than  the  weight  of  the  chips 
themselves,  it  is  advisable,  in  cases  where  there  is  not  much  fall,  to 


60  BEET-SUGAR   MANUFACTURE. 

pump  the  water  which  is  separated  from  the  chips  by  a  strainer  at 
the  lower  end  of  the  carrier,  back  to  the  upper  end.  By  this  means 
the  mass  of  exhausted  pulp  is  moved  forward  at  a  uniform  rate, 
and  the  elevator  will  consequently  work  better. 

Only  in  those  factories  where,  from  deficient  water-supply,  the 
last  diffuser  is  under  air-pressure,  is  use  of  the  hydraulic  carrier  out 
of  the  question.  In  such  cases  it  is  necessary  to  resort  to  the  use 
of  belt  or  screw  conveyors. 

Another  method  of  removing  the  chips  from  the  diffuser,  and 
which  at  the  same  time  is  connected  with  the  raising  of  the  chips, 
depends  upon  the  application  of  compressed  air  which  enters  at  the 
bottom  of  the  closed  cell.  Thereby  the  whole  mass  of  pulp  is 
thoroughly  stirred  up  and  nothing  remains  adhering  to  the  lower 
strainer.  If  meanwhile  a  slide-valve  at  the  bottom  of  the  cell  is 
opened  as  soon  as  the  pressure  has  reached  a  certain  height,  the 
whole  contents  of  the  diffuser  will  be  emptied  through  this  valve 
and  forced  through  a  pipe  to  the  pulp-press. 

For  raising  the  chips  which  are  emptied  into  the  hydraulic 
carrier,  bucket  elevators  are  commonly  used.  There  is  often  more  or 
less  difficulty  encountered  in  this  operation  on  account  of  the  buck- 
ets not  taking  up  enough  of  pulp  at  a  time;  this  difficulty  is  always 
met  with  in  those  cases  where  the  boot  of  the  elevator  is  too  large, 
and  where  the  water  is  too  deep  and  flows  too  fast.  The  evil  can  be 
immediately  remedied  by  increasing  the  water-overflow  and  making 
the  boot  smaller,  or,  still  better,  by  leading  the  hydraulic  carrier 
directly  to  the  elevator,  so  that  the  chips  go  directly  into  the  buckets. 
It  is  obvious  that  the  buckets  will  be  heavily  loaded  immediately 
after  a  diffuser  is  emptied,  while  in  the  intervals  betweenjthe  empty- 
ings the  elevator  will  have  but  little  work  to  do.  If  it  is  desired  to 
retain  the  advantages  which  a  large  boot  offers  in  giving  a  uniform 
supply  of  the  chips,  it  is  a  good  idea  to  place  in  front  of  the  elevator 
a  horizontal  shaft  provided  with  arms,  which,  as  they  revolve,  stir 
up  the  chips  from  below  and  propel  them  toward  the  elevator 
buckets. 

Besides  the  bucket  elevators,  a  screw  conveyor  is  frequently 
used  for  raising  the  chips  to  the  press,  and  serves  to  subject  the  pulp 


EXTRACTION   OF   THE   JUICE.  61 

to  a  slight  pressure.  Such  an  arrangement  works  very  well  for 
raising  the  chips,  but  is  not  very  efficient  with  regard  to  drying 
them.  Pumps  with  perforated  pressure-tubes  act  upon  the  same 
principle. 

From  the  elevators  the  chips  are  next  carried  to  a  distribution 
device  over  the  chip-presses.  Inasmuch  as  these  presses  work 
properly  only  when  they  are  kept  full  of  chips,  it  is  necessary  to 
have  a  regular  and  systematic  feed.  The  presses,  no  matter  what 
the  design,  are  placed  in  a  line,  and  the  chips  are  carried  over  them 
by  a  screw  or  rake  conveyor.  As  this  conveyor  discharges  into 
each  press  through  funnels,  every  one  will  be  kept  full  as  long  as 
the  supply  of  chips  is  sufficient.  Occasionally  those  presses  which 
get  the  residues,  and  are  consequently  unevenly  fed,  will  work 
poorly.  If  the  location  of  the  presses  permits,  it  is  desirable  to 
place  a  carrier  behind  the  last  filter-press  to  take  back  any  excess 
of  chips  to  the  elevators.  It  is  then  not  necessary  to  pay  much 
attention  to  feeding-presses,  as  the  process  regulates  itself. 

The  choice  of  chip-presses,  which  are  of  very  various  construc- 
tion, depends  upon  whether  or  not  strong  pressure  is  desired. 
For  high  pressures,  it  is  best  to  use  presses  that  have  specially 
made  mantles  and  pressure-blades.  In  all  cases  particular  atten- 
tion should  be  paid  to  having  a  strong  and  finely  perforated  plate 
strainer,  as  well  as  means  for  taking  away  the  expressed  water 
thoroughly  and  rapidly  in  such  a  way  that  it  is  impossible  for  it 
to  come  in  contact  again  with  the  chips.  The  thinner  the  layer 
of  chips  at  the  place  where  the  pressure  is  strongest,  the  greater 
the  amount  of  water  expressed. 

With  all  presses  it  is  necessary  to  allow  for  a  certain  loss,  as 
small  pieces  of  the  pulp  will  be  pressed  inevitably  through  the 
sieve.  In  order  to  avoid  loss  of  this  pulp,  the  press-water  is  carried 
back  to  the  hydraulic  carrier,  so  that  the  small  pieces  of  chips 
will  collect  in  the  main  body  and  be  returned  with  it  to  the  presses. 
If,  however,  it  is  desired  to  remove  all  the  particles  of  beet,  it  is 
necessary  to  run  the  sweet  water  and  the  chip-press  water  through 
ii  pulp  catcher  provided  with  very  fine  slits  or  holes.  The  residues 
thus  obtained,  which  are  continuously  removed  from  the  strainer 


62  BEET-SUGAR  MANUFACTURE. 

by  brushes  or  scrapers,  are  either  directly  carried  to  the  pressed 
residues  or  to  special  presses. 

With  regard  to  the  value  of  using  high  pressure  in  extracting 
chips,  opinions  differ.  It  is  a  fact  that  the  harder  the  pulp  is 
pressed,  the  greater  the  amount  of  valuable  matter  that  is  squeezed 
out  with  the  water  and  lost,  this  loss  being  greater  if  the  chips  are 
not  completely  extracted.  When  the  pulp  is  fed  directly  to 
cattle  in  the  fresh  condition,  or  when  the  pulp  is  allowed  to  sour, 
too  strong  pressing  is  to  be  avoided;  in  this  case  it  is  correct  to 
press  the  spent  slices  until  they  contain  about  10  per  cent,  of  dry 
substance. 

If,  on  the  other  hand,  the  pressed  pulp  is  to  be  dried,  the  saving 
in  fuel  must  be  compared  with  the  loss  in  nutrient  matter.  When 
fuel  is  high  it  is  rational  to  remove  as  much  of  the  water  as  pos- 
sible by  pressure,  for  in  such  cases  the  loss  in  nutriment  is  more 
than  compensated  by  the  saving  in  coal. 

Not  only  the  construction  of  the  presses  and  the  amount  of 
pressure  applied,  but  also  the  quality  of  the  slices  and  the  method 
of  diffusion  exert  influence  upon  the  proportion  of  dry  substance 
in  the  pressed  pulp.  Thin  and  quite  exhausted  slices  can  be 
pressed  better  than  thick  or  hollow  ones,  and  it  is  also  easier  to 
press  the  pulp  if  the  slices  are  fed  to  the  presses  warm  or  hot  rather 
than  cold.  On  the  contrary,  chips  which  have  been  kept  in  hot 
diffusion  for  a  long  time  are  more  difficult  to  press  than  those  which 
have  been  worked  more  quickly  or  at  a  lower  temperature.  The 
reason  for  this  is  to  be  sought  in  the  fact  that  the  cell-tissue  is 
much  swollen  after  a  short  period  of  overheating.  It  is  advisable 
to  work  with  warm  or  hot  pressure-water  in  the  diffusion,  and  to 
remove  and  press  out  the  spent  chips  while  they  are  still  warm, 
when  they  are  to  be  dried.  When,  for  any  reason,  the  exhausted 
chips  cannot  be  removed  from  the  diffusers  while  they  are  hot, 
it  has  been  recommended  to  heat  them  again  just  before  they  are 
carried  to  the  presses,  or  while  passing  through  the  upper  part 
of  the  presses,  by  means  of  hot-well  water  or  by  direct  steam. 
This  treatment,  to  be  sure,  makes  it  easier  to  press  the  chips, 
but  should  only  be  resorted  to  in  special  cases,  as  the  increased 


KXTRACTIOX    OF   THE   JUICE.  63 

amount  of  water  to  be  pressed  out  and  its  more  favorable  extrac- 
tion temperature,  increases  the  amount  of  nutriment  taken  away 
from  the  chips.  For  the  same  reason  the  addition  of  lime  to  the 
chips  is  not  desirable,  although  it  makes  pressing  easier,  since  it 
lessens  the  digestibility  of  the  fodder.  Further  hot-pressing  is 
useless  when  the  residue  is  solved,  because,  disregarding  the  loss 
in  nutriment  through  strong  pressure,  these  hot  residues  begin 
to  ferment  after  a  few  hours,  and  do  not  keep  in  silos  nearly  as 
well  as  chips  which  ferment  much  more  slowly  and  in  a  normal 
manner,  as  they  do  when  cold-pressed. 

B.    Diffusion,    Combined    with    Pressing    and     Recovery    from 

Sweet-Waters. 

Inasmuch  as  considerable  amounts  of  sugar  are  lost  in  the 
waste  waters  in  the  ordinary  diffusion  process,  it  is  easy  to  under- 
stand that  even  at  the  time  the  process  was  introduced,  attempts 
were  made  to  prevent  these  losses  by  working  the  sweet-waters 
bark  into  process.  This  resulted  in  many  difficulties;  it  was 
found,  moreover,  that  as  a  result  more  sugar  was  left  in  the  ex- 
hausted chips,  so  that  there  was  no  gain  in  the  yield  of  sugar  from 
the  same  amount  of  juice.  Consequently  this  method  of  work- 
ing was  soon  abandoned. 

Xew  incentives  to  recover  the  sugar  in  the  sweet-waters  have 
recently  arisen  in  the  difficulty  of  disposing  of  such  water  and  in 
the  preparation  of  dry  fodder.  If  the  waste  water  from  the 
diffusers  is  used  as  pressure-water,  it  is  disposed  of  in  the  simplest 
and  most  natural  way;  and,  furthermore,  considerable  economy 
in  the  fresh-water  supply  results.  The  use  of  the  waste 
water  in  this  wray  causes  a  direct  gain  only  when  the  residues  are 
dried ;  in  the  dried  chips  there  is  present  not  only  the  sugar  which 
is  otherwise  lost  in  the  waste  waters  but  also  the  total  amount 
of  non-sugars  consisting  of  easily  digestible  substances.  Only 
by  drying  is  it  possible  to  preserve  these  substances;  when  the 
residues  are  not  dried  they  sour  and  the  above-mentioned  sub' 
stances  are  converted  into  acids  and  other  matter  which  has 
little  or  no  food  value.  Such  sour  residues  have  no  greater 


G4  BEET-SUGAR  MANUFACTURE. 

value  or  nourishment  than  the  sour  residues  obtained  by  the 
ordinary  diffusion  method.  On  the  other  hand,  the  practice  of 
returning  the  sweet-water  makes  noticeably  heavier  and  better 
dry  chips  than  are  obtained  by  an  ordinary  diffusion  with  drying 
of  the  press  residues. 

Working  back  the  sweet-water  permits,  furthermore,  greater 
variety  in  the  extraction  methods  employed.  Inasmuch  as  in  this 
case  all  sugar-losses,  or  in  fact  all  losses  of  dry  substance,  are 
completely  avoided,  it  is  not  necessary  to  carry  out  the  extraction 
so  far  in  the  battery  as  in  an  ordinary  diffusion,  but  a  greater  or 
or  less  amount  of  the  juice  can  be  and  is  obtained  from  the  pulp 
presses  which  is  worked  back  either  after  the  diffusion  is  complete 
or  during  the  process.  The  greater  the  final  pressure  applied, 
the  greater  the  amount  of  sugar  which  may  be  left  in  the  chips 
when  withdrawn  from  the  diffusers  without  causing  sugar-loss 
in  the  extraction.  The  press  work,  therefore,  becomes  an  essential 
part  of  the  process  and  regulates  the  juice  extraction,  according 
as  a  greater  quantity  of  marketable  sugar  or  a  more  valuable 
fodder  is  desired,  thus  determining  whether  the  diffusion  or  the 
pressing  is  to  be  carried  further. 

The  simplest  way  of  working  back  the  sweet-water  is  wrhen 
the  usual  diffusion -battery  is  employed.  Hereby  certain  dis- 
advantages are  likely  to  result  which  must  be  guarded  against 
by  special  contrivances.  These  are  troubles  caused  by  bad 
pressure,  foaming,  and  fermentation  phenomena  of  the  sweet- 
water  in  the  battery. 

The  cause  of  bad  pressure  are  the  fine  particles  of  beet  which 
come  in  part  from  the  slicing  and  partly  from  the  presses.  The 
coarser  particles  can  be  removed  by  pulp  catchers,  but  the  fine 
particles  pass  through  the  holes  or  slits  of  the  strainer.  The 
amount  of  fine  material  is  small  at  first,  and  therefore  uninjurious. 
As  the  work  progresses,  since  none  of  the  sweet-water  is  discarded, 
the  amount  of  fine  material  increases  and  deposits  upon  the  chips 
of  the  last  receiver,  which  act  as  a  filter,  in  a  more  and  more 
dense  and  impenetrable  layer  that  serves  to  check  the  flow  of 
the  juice  and  eventually  stops  it  entirely.  It  is  easy  to  prevent 


EXTRACTION  OF  THE  JUICE.  65 

this  by  simply  drawing  off  portions  of  the  sweet-water  from  time 
to  time  and  allowing  it  to  settle. 

The  waste  diff user-water  (sweet-water),  containing  all  of  the 
pulp  particles  gradually  collected  in  its  passage  through  the  chips, 
is  run  at  regular  intervals  into  a  special  tank,  or  a  portion  of  the 
water  is  continuously  decanted  as  it  flows  in  a  slow  current 
through  the  tank.  The  fine  pulp,  settling  to  considerable  extent 
to  the  bottom,  is  pumped  with  the  surrounding  water  to  settling 
tanks  and  pressed,  making  the  bulk  of  the  top-water  containing 
but  littlo  pulp  ready  for  the  diffusion  without  further  treatment. 

The  turbid  portion  of  the  sweet-water  is  clarified  by  settling, 
the  clear  water  flowing  to  the  pressure  pumps  of  the  battery,  and 
the  pulp  finally  deposited  as  a  thick  paste  is  worked  up  either  by 
pressing  or  drying. 

The  greater  part  of  the  sweet-water  thus  is  outside  the  dif- 
fusers  only  for  a  few  minutes,  so  that  there  is  not  so  much  danger 
of  interfering  reactions  taking  place  as  would  be  the  case  if  all  the 
sweet-water  was  settled  at  one  time.  Only  about  10  per  cent,  of  the 
total  sweet-water  needs  to  be  clarified,  and  as  it  settles  sufficiently 
in  from  30  minutes  to  an  hour,  it  can  be  protected  from  change 
during  that  time  by  keeping  it  at  a  suitably  high  temperature. 

It  is  advisable,  however,  to  keep  the  water  that  is  immediately 
returned  to  the  diffusion  at  temperatures  of  at  least  50°-60°  C. 
(122°-140°  F.)  working  at  this  temperature  in  the  last  cell  and 
reheating  the  water  to  this  temperature  in  special  heaters  before 
working  it  back.  Fermentations  and  the  foaming  that  is  likely 
to  result  by  the  use  of  cold  sweet-water  are  thus  avoided. 

The  question  as  to  whether  it  is  better  to  mix  the  sweet-water 
and  the  water  from  the  presses  or  to  separate  them  according  to 
their  sugar  content  is  of  subordinate  importance.  The  amount 
of  sugar  obtained  from  the  diff  user-juice  is  determined  by  the 
amount  of  juice  and  its  density  and  the  latter  depends  upon  the 
same  factors  as  in  an  ordinary  diffusion,  namely  upon  the  length 
of  the  battery,  suitable  temperature,  as  well  as  the  nature  and 
thickness  of  the  slices.  Even  if  by  working  back  the  separated 
waters  in  the  following  order,  water  from  presses,  overflow 


66  BEET-SUGAR   MANUFACTURE. 

water,  fresh  water,  a  smaller  amount  of  sugar  is  said  to  be  re- 
tained by  the  exhausted  chips,  nevertheless  equal  results  can  be 
obtained  by  adding  a  cell  to  the  battery.  For  theoretical  reasons, 
which  are  based  upon  the  flow  of  the  juice  in  the  last  diffuser, 
it  seems  improbable  that  the  chips  actually  contain  less  sugar 
when  the  water  is  separated  than  when  the  mixed  water  is  added 
to  the  first  cell. 

The  work  with  mixed  waste  waters  is  simpler  and  more  favor- 
able as  regards  the  settling  out  of  the  pulp.  Only  one  puh> 
arrester  is  required  for  all  the  water  and  only  one  settling  tank. 
Otherwise  there  must  be  separate  collecting  tanks,  pulp  arresters 
and  clearing  tanks  for  each  different  kind  of  water  and  obviously 
there  must  be  some  arrangement  whereby  the  water  can  be  in- 
troduced into  the  battery  in  the  right  order  and  proper  amount. 

By  using  either  method,  it  is  possible  to  arrive,  within  the 
normal  limits,  at  any  desired  sugar-content  of  the  juice  or  of 
the  pressed  residues.  It  is  perfectly  clear  that  the  water  running 
off  contains  considerably  more  sugar  than  is  the  case  in  an  ordinary 
diffusion,  even  when  the  amount  of  juice  withdrawn  and  the  amount 
of  sugar  recovered  from  the  juice  is  normal.  On  an  average  the 
wraste  waters  now  contain  five  or  six  times  as  much  sugar  and  the 
pressed  chips  contain  that  sugar  which  would  otherwise  be  lost. 

When  the  work  is  normal,  the  sweet-waters  in  this  process 
contain  approximately  0.6-0.8  per  cent,  sugar  and  the  pressed  chips, 
according  to  the  pressure,  form  1-1.5  per  cent,  sugar.  This  relatively 
high  sugar-content  of  the  sweet-water,  which  makes  it  class  with 
the  thin  sirups,  shows  why  there  is  no  advantage  gained  by 
carrying  a  part  of  the  water  back;  for  just  as  much  sugar  is  lost 
as  when  all  the  water,  of  much  lower  sugar-content,  is  discarded. 
Either  all  the  sweet-water  must  be  returned  to  the  diffusion,  or 
it  is  better  to  carry  out  the  process  in  the  usual  manner,  for  a 
partial  recovery  only  makes  the  process  more  complicated  without 
materially  increasing  the  yield. 

By  lessening  the  number  of  cells  in  a  battery,  and  the 
amount  of  juice  withdrawn,  juice-extraction  is  controlled  more 
and  more  by  the  chip-presses.  In  this  way  it  is  possible  to 


EXTRACTION  OF  TlIK  JUICE.  67 

have  as  much  as  2  or  3  per  cent,  of  sugar  on  the  weight  of  the  beets 
retained  by  the  pressing  and  hence  in  the  dried  chips  and  under 
constant  working  conditions  obtain  a  product  containing  a 
uniform  amount  of  sugar. 

Besides  the  sugar,  it  is  evident  that  a  larger  amount  of  non- 
sugars  will  be  present  in  the  pressed  chips.  When  working 
with  a  normal  juice  drawing,  somewhat  less  non-sugars  are 
dissolved  out  of  the  beets  than  is  usual  in  the  diffusion  process, 
for  in  the  latter  fresh  water  is  used  to  sweeten  off,  whereas  \vhen 
the  waters  are  worked  back,  a  juice  containing  quite  a  little 
sugar  is  substituted  which  will  naturally  dissolve  less  non-sugars 
than  pure  water  will.  The  diff user-juice,  therefore,  is  always 
somewhat,  if  only  a  little,  purer  when  the  waters  are  worked 
back;  and  the  pressed  chips  contain  not  only  the  non-sugars 
which  would  otherwise  be  lost  in  sweetening  off  and  pressing,  but 
also  a  small  extra  amount  which  has  remained  undissolved. 

The  waste  waters  always  show  an  acid  reaction  which  arises 
from  acids  dissolved  from  the  cell  substance,  particularly  from 
fine  pulp.  The  degree  of  acidity  depends  upon  the  nature  of 
the  beets,  the  time  they  are  kept  outside  the  battery,  and  the 
temperature.  When  the  work  is  properly  carried  out,  the  acidity 
does  not  increase,  but  varies  within  narrow  limits.  It  has  no 
influence  upon  the  diff  user  work  or  the  quality  of  the  juice, 
although  it  is  true  that  in  some  seasons  the  strainers  of  the 
filter-presses,  and  the  pumps,  may  be  acted  upon  more  than 
ordinarily.  If  this  is  found  to  take  place  often,  it  is  best  to  use, 
brass  or  bronze  to  replace  the  worn  parts.  / 

To  obviate  difficulties  formerly  encountered  when  the  waters 
were  carried  directly  back,  it  has  been  proposed  to  defecate  such 
waters  with  lime;  to  carbonatate  until  neutral,  and  then  to  filter. 
In  this  way  it  is  evident  that  the  small  particles  of  pulp  which 
r,rc  likely  to  impede  the  flow  of  the  juice  will  be  removed  most 
jfficiently  and  the  water  will  keep  better.  It  appears,  however, 
very  questionable  whether  the  gain  is  worth  the  expense  involved 
in  building  an  entirely  new  and  extensive  defecation,  saturation 
and  filter-press  equipment,  as  well  as  the  operation  cost. 


68  BEET-SUGAR   MANUFACTURE. 

Furthermore,  it  must  not  be  forgotten  that  defecation  causes 
the  removal  of  considerable  quantities  of  valuable  nutriment 
which  when  lime  is  not  used  would  pass  into  the  spent  chips  and 
be  retained  in  the  fodder.  Again,  purer  juice  is  not  extracted 
by  this  method,  as  those  substances  which  are  removed  by  thin 
special  defecation  ordinarily  would  be  retained  by  the  chips  or 
removed  when  the  juice  is  defecated. 

Besides  the  waste  waters  from  the  diffusers,  the  sweet-waters 
from  the  filter-presses,  or  from  the  boneblack  filters,  where  still 
used,  can  be  worked  back  in  the  diffusers  by  substituting  this  for 
'fresh  water,  which  would  otherwise  be  necessary.  By  a  very 
slight  increase  in  the  juice  drawings  the  sugar  otherwise  lost  in 
sweetening  off  can  be  recovered  in  the  juice  and  the  cost  of 
evaporation  lessened. 

Juice  extraction  by  alternate  diffusion  and  pressing,  like 
working  back  sweet-waters  in  diffusion,  has  already  been  much 
recommended,  but  it  is  only  quite  recently  that  the  so-called 
"press  diffusion  "  has  been  used  in  actual  practice. 

The  apparatus  required  is  one  that  works  continuously;  it 
consists  of  a  number  of  separate  members,  each  of  which  has  a 
diffuser  and  a  press  compartment,  all  being  connected  directly 
together  without  valves  or  piping.  In  the  press  compartment 
there  is  a  pressure-screw  which  serves  to  express  the  chips  and 
at  the  same  time  force  them  into  the  diffuser  compartment;  the 
latter  forms  the  connecting-chamber  to  the  next  cell.  In  this 
connecting-chamber  the  chips  which  have  just  been  subjected  to 
pressure  come  into  contact  with  the  juice  from  the  following 
pressure-screw;  the  juice  penetrates  through  the  chips  and  is 
thoroughly  mixed  in  by  a  stirrer  and  carried  to  the  next  pressure- 
chamber.  Thus  the  chips  travel  upwards  through  the  apparatus, 
which  is  vertical,  passing  up  through  all  the  other  cells  of  the 
battery  until  they  leave  the  last  pressure-screw  wrell  pressed  and 
more  or  less  desugarized.  The  water  required  for  the  process 
enters  under  pressure  in  the  outer  chamber  of  the  last  press, 
the  chips  coming  from  the  screw  making  a  seal.  The  juice  flows 
through  the  apparatus  in  the  opposite  direction  to  which  the 


J:\TIIACTIOX  OF  THE  JUKI.  69 

chips  are  moving,  leaving  the  last  member  in  a  concentrated 
condition. 

This  "press  diffusion"  has,  in  many  respects,  great  advan- 
tages compared  with  ordinary  diffuser  work.  A  continuous 
process  is  always  advantageous.  All  valves  and  arrangements 
for  emptying  are  unnecessary ;  there  are  no  waste  waters,  as  they 
are  immediately  forced  onward,  as  fast  as  they  are  formed,  by 
the  fresh  water;  the  desugaring  of  the  chips  must  take  place 
much  more  quickly,  because  the  diffusion  is  aided  by  the  pressing 
and  the  juice  is  drawn  off  in  a  very  concentrated  condition. 

The  complicated  mechanism  required  for  the  above  process 
must  be  reckoned  as  a  disadvantage.  The  ordinary  diffusion 
work  has  the  great  advantage  that  is  it  not  dependent  upon  any 
means  of  mechanical  transportation ;  it  is  only  necessary  to  provide 
arrangements  for  feeding  the  cells  with  chips  and  for  removing 
the  spent  material,  and  at  every  station  where  the  juice  is  to  be 
drawn  off  very  simple  arrangements  suffice,  being  in  sight  and 
easily  accessible.  In  the  " press  diffusion"  the  transporting 
arrangements,  the  pressure-screws,  and  the  stirring-apparatus,  are 
entirely  enclosed;  in  order  to  get  at  them,  it  is  necessary  to  put 
the  whole  apparatus  out  of  action  and  partly  empty  it. 

According  to 'present  experience  with  pressure-screws,  they 
only  work  well  and  uniformly  when  regularly  fed.  It  is  doubtful 
whether  it  is  possible  in  "press  diffusion"  to  always  satisfy  this 
condition,  particularly  when  the  apparatus  consists  of  eight  cells, 
more  or  less,  and  the  customary  extraction  is  desired. 

The  amount  of  power  required  for  "press  diffusion"  is  con- 
siderable and  increases  with  the  number  of  units  employed. 

As  regards  the  wear  of  the  different  parts  of  the  apparatus, 
particularly  the  strainers  and  the  pressure-screws,  there  are  at 
present  no  data;  it  should  be  noticeable  in  the  course  of  time. 
There  are  no  results  of  factory  experience  available  from  which 
an  adequate  opinion  could  be  based,  but  there  is  no  reason  for 
doubting  that  results  can  be  obtained  by  this  process,  as  regards 
purity  of  juice  and  quality  of  pressed  chips,  equal  to  those  of 
diffusion,  utilizing  sweet-waters. 


70  BEET-SUGAR  MANUFACTURE. 

C.  Extraction  by  Pressure. 

While  in  earlier  pressure  methods  the  sole  object  was  to  get 
as  high  a  sugar-content  as  possible  in  the  juice,  the  modern 
processes  work  also  for  pure  juice  by  simple  expression  in 
ordinary  presses,  but  besides  make  a  fodder  rich  in  sugar  and 
nutriment. 

In  its  original  form,  the  "  Scalding  Process,"  as  it  is  commonly 
called,  was  carried  out  by  mixing  finely  divided  beets  with  four 
or  five  times  their  volume  of  extracted  juice,  heated  to  about 
100°  C.  (212°  F.),  so  that  the  beets  were  at  once  brought  to  a 
uniform  temperature  of  about  80°  C.  (176°  F.).  By  this  means 
it  was  supposed  that  cells  were  burst,  but  that  no  diffusion 
which  was  considered  injurious  could  take  place  since  the  scalding 
juice  always  had  about  the  same  density  as  that  in  the  beets. 

In  practice  this  process  was  not  satisfactory,  because  the  con- 
centrated juice  (as  high  as  20°  Brix)  foams  too  much  and  too 
much  sugar  remains  in  the  pulp  residue.  As  now  worked,  the 
process  is  somewhat  different.  The  beets  are  cut  into  slices 
about  two  millimeters  thick  and  immediately  fall  into  a  stream 
of  six  or  seven  times  their  volume  of  hot  juice,  by  which  they  are 
carried  along  in  a  scalding  trough  of  special  design. 

In  the  latter  a  constant  temperature  of  from  80°  to  85°  C. 
(176°  to  185°  F.)  is  maintained  by  passing  the  jui^e  stream, 
which  carries  the  slices,  through  a  heater.  Behind  the  scalding- 
tank,  the  particles  of  beet  are  removed  by  a  perforated  screw 
through  which  the  juice  passes  while  the  slices  are  being  sub- 
jected to  slight  pressure.  While  still  hot  the  slices  pass  into  the 
the  slice-press  in  which  they  are  pressed  to  30-35  per  cent,  dry 
substance  and  10  per  cent,  sugar.  The  expressed  juice  passes 
through  a  foam  remover,  in  which  the  foam  is  removed  by 
means  of  steam  or  water,  and  then  to  the  scalded  juice.  Pulp 
and  sand  eliminators  are  also  placed  in  the  piping.  By  introduc- 
ing fresh  water,  or  sweet-water,  into  the  filter-presses,  the  juice 
is  kept  at  14°  to  15°  Brix,  or,  in  other  words,  to  about  the  same 
density  as  diff user-juice. 


EXTRACTION'  OF  THE  JUICE.  71 

It  is  obvious  from  the  above  that  the  process  carried  out  in 
this  manner  is  no  longer  one  of  simple  pressing,  but  is  combined 
with  a  true  diffusion.  It  is  different  from  the  processes  already 
described  only  as  regards  the  degree  and  method  of  effecting  the 
diffusion.  In  those  cases  where  the  scalding  process  is  carried 
out  side  by  side  with  an  ordinary  diffusion,  it  is  customary  to 
carry  the  diff user-juice  wholly  or  partly  through  the  scalding- 
trough,  using  it,  therefore,  for  the  further  enrichment  of  the 
juice. 

The  amount  of  crude  juice  depends  upon  the  dilution  and  the 
pressing;  it  varies  from  80  to  95  parts  for  100  parts  by  weight 
of  beets  and  is  from  10  to  20  parts  less  than  in  the  usual  diffusion 
process.  The  purity  of  the  juice  is  a  little  better  than  that  of 
a  normal  diffusion,  inasmuch  as  a  somewhat  greater  amount  of 
non-sugars  remains  together  with  the  sugar,  in  the  pressed 
residues.  The  increase  in  purity  amounts  to  from  one  to  two 
percent.,  according  to  the  nature  of  the  beets,  the  degree  of  heat- 
ing, and  the  amount  of  pressure  applied.  After  defecation,  the 
difference  in  purity  becomes  much  less,  because  defecation  of  the 
diff  user-juice  causes  the  removal  of  more  impurities  than  does 
defecation  of  the  scalded  juice. 

The  ready  compressibility  of  the  scalded  slices,  as  has  already 
been  pointed  out,  is  not  due  to  the  fact  that  the  cell  has  been 
burst  so  much  as  to  the  fact  that  the  cells  have  been  killed.  It 
is,  consequently,  a  matter  of  indifference  whether  the  heating 
of  the  sliced  beet  takes  place  suddenly,  or  gradually  during  ten 
minutes,  as  in  the  case  of  ordinary  diffusion.  The  method  of 
working,  therefore,  could  be  changed  without  any  resulting  injury 
to  the  compressibility,  so  that  the  slices  would  be  gradually 
heated  to  a  temperature  of  from  70°-SO°  C.  (158°-176°  F.). 
To  the  favorable  effect  of  the  sudden  heating  has  been  ascribed 
the  immediate  killing  of  all  the  bacteria;  but  inasmuch  as  these 
must  also  lose  their  activity  when  the  heating  takes  ten  minutes, 
no  advantage  is  gained.  Furthermore,  it  is  a  matter  of  fact 
that  the  compressibility  of  the  scalded  slices  is  not  one  bit 
better  than  that  of  diffuser-chips  which  have  lain  for  more  than 


72  BEET-SUGAR  MANUFACTURE. 

an  hour  in  juice  at  from  60°-SO°  C.  (140°-176°  F.).  In  the 
diffuser-chips,  however,  there  is  only  water,  or  a  very  thin  sirup, 
whereas  a  much  more  concentrated  sirup  remains  in  the  scalded 
slices.  The  dried  substance,  being  15-17  per  cent,  of  the  weight 
of  the  residues  from  the  ordinary  process  when  well  pressed, 
is  increased  to  30-35  per  cent.  Reckoned  on  the  original  weight 
of  the  beets,  there  are  25-30  per  cent,  of  "sugared  slice"  residues 
which  give  10-11  per  cent,  when  dried,  these  latter  containing 
90  per  cent,  of  dried  substance  and  30-40  per  cent,  of  sugar. 

The  work  according  to  this  process  is  very  simple  and  requires 
less  attention  than  diffusion;  although  the  slice-presses  must  be 
carefully  watched  to  see  that  the  expression  is  uniformly  good. 
Every  cessation  of  work  must  be  carefully  avoided,  because  if  the 
slices  remain  too  long  in  hot  juice  at  a  temperature  of  90°— 
100°  G.  (194°-212°  F.),  they  become  soft,  swell  up,  and  are 
hard  to  press. 

The  real  advantages  of  the  scalding  process  lie  in  obtaining 
somewhat  purer  massecuites,  in  the  possibility  of  working  up 
larger  amount  of  beets  in  the  same  amount  of  time,  and  in  the 
economy  of  coal  consumption  as  compared  with  diffuser  work 
combined  with  drying  the  chips.  The  amount  of  space  required 
for  the  drying  of  the  chips  is  also  less  on  account  of  their  relatively 
larger  amount  of  total  solids.  Of  course  a  greater  yield  of  sugar 
in  the  juice  and  dry  products  cannot  be  obtained  by  the  press 
over  diffusion,  or  by  the  diffusion  battery  where  the  sweet-waters 
are  worked  back,  although  it  is  evident  that  the  yield  will  be 
greater  than  in  the  case  of  ordinary  diffusion  where  the  sweet- 
waters  are  discarded. 

As  disadvantages  of  the  process  should  be  considered  the 
large  amount  of  power  required  for  the  presses,  and  the  fact  that 
it  is  in  all  cases  necessary  to  leave  a  large  amount  of  sugar  in  the 
expressed  slices.  It  is,  therefore,  impossible  in  seasons  when  the 
price  of  sugar  is  high  and  the  value  of  the  fodder  low,  to  so  change 
the  manner  of  working  that  more  sugar  is  obtained  in  the  juice. 
In  this  respect  the  scalding  process  is  less  adaptable  than  press- 
diffusion,  or  ordinary  diffusion  with  return  of  the  sweet-waters. 


EXTRACTION  OF    THE  JUICE.  73 

Inasmuch  as  the  yield  of  dry  chips  in  the  scalding  process  is 
almost  twice  as  much  as  in  the  case  of  diffusion,  the  profit  in  the 
scalding  process  depends  chiefly  upon  the  market  value  of  the 
"sugar-slices."  According  to  their  chemical  composition,  they 
should  be  worth  about  10  per  cent,  more  than  ordinary  dried  chips. 
At  this  rate  it  is  impossible  to  earn  more  by  the  process  than  by 
diffusion  with  return  of  the  sweet-waters  and  drying  the  chips. 
It  i.s  .<till  a  debatable  question  whether  " sugared  chips"  as  fodder 
arc  worth  more  as  fodder,  on  account  of  favorable  digestive 
effects,  than  their  composition  would  indicate.  The  future  of 
the  process,  therefore,  depends  upon  the  final  decision  on  this 
last  question  and  on  that  of  the  fodder  value  of  sugar  for  different 
animals. 

A  modification  of  the  scalding  process,  in  such  a  way  that 
more  sugar  is  obtained  in  a  marketable  form,  consists  in  mashing 
the  press  residues  after  the  first  pressing  with  hot  sirups  and 
then  subjecting  them  to  another  pressing  after  draining  them 
as  completely  as  possible.  The  dilute,  impure  sugar  solution 
then  mixes  very  quickly  with  the  much  purer  juice  which  remains 
in  the  residues ;  the  latter  take  up  the  sirup  and  yield  a  somewhat 
purer  juice,  so  that  the  final  result  of  the  treatment  is  a  purer 
sirup  and  residues  which  contain  considerably  more  of  the  im- 
purities of  the  sirup.  This  method  of  treatment,  however, 
causes  the  loss  of  some  of  the  advantages  which  are  character- 
istic of  the  scalding  process,  namely,  low  expense  of  evaporation 
and  production  of  an  unmixed,  unadulterated,  dry  fodder  con- 
taining only  the  unchanged  constituents  of  the  beet. 


CHAPTER   V. 
DRYING  THE  SPENT  CHIPS. 

THE  question  of  drying  the  spent  chips  from  ordinary  diffusion 
is  still  not  settled  for  all  conditions.  It  is  an  entirely  agricul- 
tural one.  In  many  sugar-houses  the  farmers  take  away  the 
moist-press  residues,  preferring  fresh  or  ensilaged  fodder  to 
dry.  In  such  cases  the  sugar  manufacturer  has  to  govern 
himself  entirely  by  the  wishes  of  the  contracting  farmers;  but 
if  he  grows  his  own  beets,  he  should  let  figures  decide  the  matter 
by  making  exact  estimate  of  cost  of  equipment  and  the  advan- 
tages and  disadvantages  of  the  fodders  in  his  special  case.  Chief 
to  be  considered  in  such  reckoning  is  the  saving  in  transporta- 
tion and  freight  by  drying  chips  and  the  loss  in  food  material 
caused  by  ensilage.  This  is  greater  the  higher  the  temperature 
at  time  of  pressing  and  storing  the  chips,  the  less  care  taken 
in  storing  them  properly,  the  more  sugar  they  contain,  and  the 
longer  they  are  kept  in  storage. 

In  the  ordinary  method  a-nd  period  of  ensilage,  the  average 
loss  in  weight  and  nutriment  can  be  estimated  as  one-third. 
Speaking  generally,  it  will  be  found  advantageous  to  dispose  of 
the  fodder  fresh  during  the  campaign,  drying  the  larger  part 
remaining. 

Sugary  residues,  such  as  obtained  by  working  back  sweet- 
water  from  diffusion  or  from  the  scalding  process,  obviously 
must  be  dried.  In  these  processes,  a  drying  equipment  is  a 
necessary  addition  to  the  plant. 

The  drying  apparatus  either  work  by  direct  firing  or  by  steam 
heat.  In  the  former,  the  hot  flue-gases  act  directly  on  the 
chips;  in  the  latter,  steam  is  used  for  the  heating-surfaces.  In 
ooth  cases  the  drying  is  aided  by  a  strong  air-current  from  fans. 

74 


J)RY!XG  THE  SPENT  CHIPS.  75 

For  drying  with  flue  gases,  either  ovens  or  revolving-drums 
are  used;  the  former  have  trough-shaped  masonry  floors  in  which 
are  paddles  which  work  the  mass  over  and  over  as  it  is  moved 
along. 

The  ovens  are  seldom  built  on  a  level,  but  usually  are  in 
stories,  one  above  the  other.  The  furnace,  which  is  on  top,  is 
fed  with  cheap  coal,  coke,  or  lignite,  the  draught  being  forced, 
so  that  the  hot  gases  are  practically  smokeless,  their  temperature 
being  not  over  S00°-10000  C.  (1500°-1800°  F.). 

The  gases  pass  back  of  the  bridge-wall  and  come  in  direct 
contact  with  the  chips  and  pass  over  them  in  the  same  direction 
in  which  they  are  moving  over  all  of  the  shelves,  which  are 
invariably  three  deep.  At  once  there  is  a  large  temperature 
drop,  because  the  evaporation  from  the  wet  chips  and  consequent 
heat  absorption  is  very  great.  At  the  end  of  the  first  shelf  the 
gases  are  only  at  200°-250°  C.  (400°-500°  F.)  and  at  their  exit 
70-100°  C.  (160-212°  F.)  according  to  the  demands  placed  upon 
the  oven. 

By  the  simultaneous  action  of  the  paddles  of  the  carrier, 
which  toss  them  up  and  clown  as  well  as  shove  them  onward,  and 
the  strong  air  blast,  the  chips  pass  through  the  oven  in  about 
half  an  hour,  the  lighter  parts  more  quickly  and  the  smaller  and 
wetter  portions  more  slowly.  With  a  water-content  of  6-12  per 
cent,  they  drop  in  regular  manner  from  the  lower  shelf  into  a 
screw-conveyor  and  pass  out  of  the  oven. 

The  control  of  the  apparatus  is  simple  enough  with  ordinary 
care.  Of  chief  importance  is  regularity  in  feeding  and  expressing 
the  chips.  Aside  from  this  the  heating  only  requires  to  be 
regulated  so  that  the  gas  temperature  at  the  end  of  the  first  shelf 
is  200C-250°  and  at  the  exit  ah  ;ut  80°-90°.  If  there  is  a  quick 
rise  of  temperature  at  the  end  of  the  first  compartment,  it  is  a 
sign  that  the  feeding  of  the  chips  is  inadequate.  This  should 
be  increased  immediately,  or  if  the  supply  fails,  the  fire  doors 
must  be  opened  and  the  draught  shut  off  so  that  the  hot  gases 
escape  directly  into  the  air.  It  is  also  important  that  the 
capacity  of  the  fan  is  suited  to  that  of  the  oven,  in  order  to  insure 


76  BEET-SUGAR  MANUFACTURE. 

proper  dryness  in  the  finished  chips.  With  a  little  experience, 
this  can  be  readily  determined  by  feeling  of  them  with  the  hand. 

The  strong  draught  carries  away  fine  particles  of  the  chips, 
which  can  be  quite  recovered  by  using  a  dust  catcher,  but 
the  amount  is  small,  perhaps  2-3  per  ceut  of  the  dried  product. 

In  the  drum  drying-apparatus  the  chips  enter  simulta- 
neously with  the  hot  gases,  passing  through  one  or  more 
drums,  and  are  kept  in  motion  by  the  revolution  of  the 
drum.  The  difference  between  the  different  drum  systems  lies 
in  different  methods  of  feeding  the  chips  and  of  introducing  the 
hot  gases.  As  each  individual  drum  or  system  of  drums  must  be 
specially  heated  and  fed  with  chips,  while  an  oven  with  a  capacity 
of  several  drums  requires  only  one  fire  and  one  place  for  feeding 
chips,  it  is  easy  to  understand  why  there  is  more  attention 
required  in  keeping  the  drums  filled  with  chips  and  the  tem- 
perature right  than  for  the  oven,  and  furthermore  the  uniformity 
of  heating  which  results  from  the  massiveness  of  the  oven  is  lost. 
Lack  of  sufficient  attention  in  the  case  of  drum-drying  is  much 
more  likely  to  result  in  the  overheating  the  chips,  or  exposing 
them  too  long,  or,  on  the  other  hand,  the  pulp  is  often  not 
sufficiently  dried.  In  the  latter  case  it  will  not  keep  nearly  as 
well.  If  these  evils  are  avoided,  it  is  possible  to  obtain  very 
satisfactory  results  from  drum-drying. 

Drying  by -steam  is  accomplished  •  in  jacketed  troughs  which 
are  built  one  over  another  and  which  are  enclosed  in  iron  com- 
partments. Bundles  of  pipes  provided  with  paddles  revolve  in 
the  troughs  to  stir  up  the  minced  chips  and  move  them  along, 
tossing  them  against  the  hot  pipes.  The  jackets  are  heated  by 
exhaust,  the  pipes  by  live  steam.  The  water-vapors  expelled 
from  the  pulp  are  removed  by  suction,  and  by  means  of  the 
latter  considerable  amounts  of  hot  air  are  brought  into  contact 
with  the  pulp,  thus  hastening  the  evaporation.  Dust  catchers 
are  used  to  pervent  fine  material  going  through  the  suction-fans. 
For  steam  drums  to  be  efficient,  it  is  necessary  that  the  chips  be 
minced  in  a  hashing  machine.  The  temperature  prevailing  in 
the  ovens  while  in  operation  is  under  100°  C.,  and  in  the  troughs 


DRYING   THE   SPENT  CHIPS.  77 

the  heat  can  scarcely  exceed  this  figure  even  when  the  apparatus 
is  stopped.  Consequently  there  is  no  danger  of  the  pulp  being 
injured  in  any  way  through  carelessness,  for  the  temperature 
even  in  the  steam-pipes  is  not  high  enough  to  cause  browning; 
the  chips  retain  their  natural  color  and  porous  structure,  in 
contrast  to  those  which  are  dried  by  direct  heat,  which  are 
always  darker-colored  and  harder. 

Although  there  is  no  danger  of  burning  in  drying  by  steam, 
yet  the  process  requires  care.  If  the  feeding  is  not  regular, 
the  product  is  now  too  dry,  now  too  moist.  In  the  first  case, 
the  steam  consumption  is  excessive,  the  heat  passing  off  in  the 
air  which  is  sucked  through.  In  the  latter  case,  the  chips  will 
spoil  and  must  be  redried. 

Compared  with  fire-drying,  steam-drying  has  the  disad- 
vantage that  the  process  cannot  be  forced  and  the  operating 
cost  is  higher.  Since  the  steam  has  to  be  produced  by  a  separate 
furnace  and  a  part  is  wasted  in  heating  the  air  sucked  through 
the  apparatus,  the  steam  process  evidently  uses  more  coal.  On 
the  other  hand,  cheaper  fuel  can  be  used.  The  equipment  for 
steam-drying  costs  more  and  therefore  the  capital  invested  is 
greater,  but  there  has  been  too  little  experience  to  judge  of 
cost  of  maintenance.  The  advantage  of  steam-drying  lies  in 
the  fact  that  a  superior  product  is  obtained,  so  that  in  many 
places  it  would  be  preferred  in  spite  of  the  greater  initial  cost. 

A  multiple  use  of  heat  is  not  possible  either  in  steam-  or 
fire-drying.  Therefore  the  aim  should  be  merely  to  utilize  as 
much  of  the  direct  heat  from  the  fuel  as  possible.  In  the  case 
of  direct  drying  it  has  already  been  found  possible  to  utilize 
80  per  cent,  of  the  total  heat  produced  from  the  fuel,  although 
this  economy  has  resulted  somewhat  at  the  expense  of  the 
character  of  the  dried  beet-chips;  their  appearance  improves  in 
proportion  to  the  amount  of  air  introduced  during  the  drying 
and  to  the  lowness  of  the  initial  temperature;  both  of  these 
conditions  correspond  to  a  waste  of  fuel. 

The  kind  of  fuel  and  the  manner  of  firing  affects  the  color 
of  fire-dried  chips.  Firing  with  coke,  which  obviously  is  too 


78  BEET-SUGAR  MANUFACTURE. 

dear;  and  with  lignite,  gives  the  lightest-colored  chips.  Of 
anthracite  coals,  only  uninflammable  dustless  nut-coal  is  suitable, 
and  this  ought  to  be  sprinkled  with  water  before  being  put  in  the 
furnace.  To  keep  the  fine  ash  out  of  the  chips  there  should  be 
a  large  space  behind  the  bridge-wall  to  allow  the  ash  to  settle 
and  be  drawn  off,  most  conveniently  by  a  drain.  Automatic 
stokers  work  very  well. 

In  order  to  save  fuel,  it  has  been  proposed  to  utilize  the  heat 
of  the  spent  boiler-flue  gases  in  a  special  drying-apparatus,  or 
for  preliminary  driers  to  the  drying-ovens.  A  simple  calculation 
will  show  that  the  heat  of  the  boiler  gases  is  barely  sufficient  to 
dry  50  per  cent,  of  the  chips.  How  the  quality  of  the  chips  would 
be  affected  by  such  gases,  full  of  soot  and  fine  ashes,  has  not  yet 
been  found  out.  It  is,  therefore,  not  possible  to  say  whether 
this  method  would  have  practical  advantages.  Experience  has 
shown  that  only  moist  beet-chips,  continually  moving,  can  be 
brought  in  direct  contact  with  hot  combustion-gases.  Dried 
chips  continue  to  grow  more  or  less  brown,  and  the  danger  of 
burning  is  great.  Boiler-flue  gases  can  be  used  to  advantage 
in  steam-drying  apparatus,  but  the  necessary  construction  would 
be  too  expensive. 

What  has  been  said  concerning  the  drying  of  chips  from  the 
ordinary  diffusion  process  applies  also  to  the  " sugared"  chips 
of  other  processes. 

The  question  has  never  been  definitely  settled  in  regard  to  the 
changes  in  the  composition  of  the  spent  beet-pulp  which  take  place 
during  drying.  The  sugar  apparently  remains  almost  entirely 
unchanged,  at  least  if  the  firing  is  so  conducted  that  the  dried 
slices  keep  light  colored.  The  digestibility  of  the  other  con- 
stituents do  not  seem  to  have  suffered  noticeably  either  in  fire- 
or  steam-drying,  except  the  albumins  which  are  affected  if  the 
heat  has  risen  above  120°-130>  C.  (2.-)00-270°  F.).  Hence  the 
digestibility  of  browned  or  slightly  scorched  chips  is  always 
perceptibly  influenced.  In  normal  work  there  will  be  no 
scorching,  as  the  slices  never  attain  the  temperature  of  the 
surrounding  gases,  especially  at  their  entrance,  where  they  still 


DRVIXCi   Till:   *PENT  CHIPS.  79 

hold  much  water.  The  vaporization  is  so  rapid  that  the  chips 
never  get  beyond  boiling  temperature.  Feeding  experiments 
comparing  fire-  and  steam-dried  slices  show  that  while  the 
digestibility  of  the  organic  material  as  a  whole  is  somewhat 
greater  in  the  latter,  the  albumins  in  the  former  show  a  higher 
digestibility  number.  These  results  are  not  altered  in  the  case 
of  rather  dark-colored  " sugared"  chips  which  make  a  darker, 
moister  product  as  the  dark  color  is  found  to  be  due  to  but 
minute  traces  of  decomposed  sugar. 

When  soaked  in  water  the  steam-dried  slices  swell  up  quicker 
and  take  up  more  water  than  the  fire-dried  product,  but  this 
is  in  part  due  to  the  mincing  to  which  the  former  have  been 
subjected. 

The  ash-content  of  the  directly  dried  chips,  calculated  upon 
the  basis  of  dry  substance,  is  always  higher  than  that  of  the 
.-team-dried  chips,  because  the  former  are  always  contaminated 
with  a  little  chimney -ash. 

The  increase  is  at  most  but  small,  seldom  0.5-1%  of  the 
dried  substance.  The  freer  the  dried  slices  are  from. dust  the 
better  the  fan  works,  hence  the  less  ash;  all  of  which  is  dependent 
on  the  efficiency  of  the  dust-catcher. 

The  amount  of  dried  product  obtained  from  100  parts  of  beets 
depends  upon  the  amount  of  pulp  and  upon  the  method  of  juice 
extraction.  By  the  scalding  process  the  yield,  as  already  shown, 
according  to  the  juice  concentration,  is  9-11  per  cent,  "sugared" 
(hips,  these  containing  30-40  per  cent,  of  sugar.  The  ordinary 
diffusion  process  gives  5  to  6  per  cent.,  according  to  the  amount 
of  dry  substance  lost  in  the  press-waters,  and  to  the  care  exercised 
in  catching  the  pulp  particles.  These  latter  chips  usually  contain 
2-5  per  cent,  of  sugar.  Using  diffusion  with  recovery  of  sweet- 
waters  the  yield  of  dry  chips,  according  to  the  lixiviation,  lies 
between  the  limits  mentioned. 

If  a  properly  working  dust-catcher,  such  as  the  "cyclone," 
is  installed  behind  the  fan,  loss  in  chip  substance  is  at  an  end. 
The  fine  pulp  particles,  contaminated  with  20-25  per  cent,  of  ash, 
will  be  entirely  trapped.  The  amount  of  this  chip  dust  is  trifling, 


80  BEET-SUGAR  MANUFACTURE. 

about  2  to  3  per  cent,  of  the  dried  product.  This  material  makes 
a  good  fodder  when  mixed  with  molasses,  as  it  contains  at  least 
75-80  per  cent,  of  pulp  substance,  but  owing  to  a  large  mineral 
content  it  should  be  fed  only  to  animals  with  good  digestions. 

The  keeping  qualities  of  the  dried  residue  are  excellent, 
provided  the  drying  has  been  thorough  and  uniform  and  the 
water-content  is  not  more  than  12-14  per  cent.,  and  it  is  stored 
in  a  dry  place.  When  stored  in  moist  places  and  against  damp 
walls  mold  is  very  likely  to  form.  Dried  chips  which  are  carried 
to  a  low  water-content  take  up  water  again  from  the  air  till 
the  percentage  becomes  12-14,  with,  of  course,  a  corresponding 
increase  in  weight.  Twelve  to  14  per  cent  is  in  fact  the  normal 
water-content  of  not  only  air-dried  beet-chips  but  that  of  most 
dried  organic  material.  "  Sugared  "  chips  should  be  cooled  before 
storing,  cooling-drums  being  used  for  this  purpose. 

Frequently  the  pressed  chips,  while  still  moist,  are  treated 
with  hot  molasses  before  fire-drying  them,  from  four  to  five 
parts  of  molasses  being  added  to  about  300  parts  of  pressed  chips, 
or  the  proportion  originally  present  in  the  beets.  The  molasses 
is  sucked  up  very  quickly  by  the  pressed  chips,  and  the  drying 
takes  place  in  the  usual  way,  although  a  slight  caramel  formation 
cannot  be  avoided,  because  the  molasses  collects  mostly  on  the 
outer  layers.  It  is  better  to  make  "  molasses  chips "  by  mixing 
the  molasses  into  the  dried  chips  as  they  come  from  the  oven, 
still  warm.  The  molasses  is  quickly  absorbed  by  both  classes 
of  chips,  if,  of  course,  they  are  warmed  to  70°-90°  C.  (160°- 
195°  F.).  Molasses  can  be  worked  into  the  dried  chips  up  to 
half  their  weight  or  more  and  a  dry  fodder  results  which  is  easily 
preserved  and  handled.  It  contains  20-2.5  per  cent,  of  sugar 
and  is  worth  a  good  deal  more  than  the  "  sugared  "  chips. 


CHAPTER  VI. 

THE  PRELIMINARY  PURIFICATION  AND  WARMING  OF  THE 
DIFFUSION-JUICE. 

The  raw  diffusion -juice  as  it  comes  from  the  diffuser  is  a  pale- 
yellow  or  grayish-colored,  turbid  liquid  which  very  quickly  turns 
dark  on  exposure  to  the  air,  so  that  after  a  few  minutes  it  becomes 
almost  black.  This  blackening  is  caused  by  the  oxidizing  action 
of  certain  enzymes  (oxydases)  on  a  constituent  of  the  juice 
such  as  ty rosin.  This  juice  contains  practically  all  of  those  sub- 
stances which  were  dissolved  in  the  beet  and  which  have  been 
extracted  from  it  by  diffusion.  U6-9S  per  cent,  of  the  sugar  in 
the  beet  is  extracted  ordinarily.  The  following  approximate 
amounts  of  non-sugars  go  into  solution:  of  the  ash,  65  per  cent.; 
alkalies,  sulphuric  and  phosphoric  acids,  and  chlorine,  70-80  per 
cent.:  lime,  alumina,  and  ferric  oxide,  20  per  cent.;  protein 
nitrogen,  15-25  per  cent.;  other  nitrogenous  matter,  90  per  cent. 
The  non-sugars  go  into  solution  in  proportion  as  they  are  present 
in  the  beets. 

The  non-sugars  which  are  not  removed  by  the  defecation  and 
carbonatation  of  the  juice  can  be  termed  the  injurious  non- 
sugars,  as  they  lessen  the  sugar  yield.  Of  course,  it  should  be 
noted  that  precipitable  non-sugars  are  also  injurious  in  so  far  as 
they  cause  factory  troubles,  such  as  poor  filtration  and  scale 
in  vacuum  apparatus.  The  really  injurious  non-sugars  as  defined 
are  alkalies  and  soluble  non-protein  nitrogenous  matter.  Ordi- 
narily the  density  of  the  juice  lies  between  12  to  15  degrees,  Brix, 
corresponding  to  from  10  to  13  per  cent,  of  sugar.  The  nature 
of  the  organic  non-saccharine  constituents  is  for  the  most  part 
unknown;  all  that  is  established  is  that  for  100  parts  of  sugar 
there  are  from  2  to  2J-  parts  of  albumin,  2J  to  3  parts  of  other 

81 


82  BEET-SUGAR    MANUFACTURE. 

nitrogenous  matter,  ^  to  1  part  of  reducing  substances,  1  part 
pcntosans,  and  0.4  to  0.8  part  of  oxalic  acid.  The  inorganic 
constituents  are  chiefly  potash,  with  some  soda,  lime,  magnesia, 
phosphoric  acid,  sulphuric  acid,  chlorine,  and  small  amounts  of 
other  acids  and  bases.  The  crude  juice  always  shows  an  acid 
reaction,  this  acidity  corresponding  to  1-2  c.c.  of  normal  acid  in 
100  c.c.  of  juice. 

The  preliminary  purification  serves  to  remove  all  the  pulp  and 
fibres  of  beet  which  are  mechanically  carried  through  the  strainers 
with  the  juice,  and  furthermore  to  precipitate  a  part  of  the  dis- 
solved matter  previous  to  defecation. 

The  removal  of  the  stray  pulp  and  fibres  previous  to  defecation 
is  something  that  should  never  be  omitted  nor  its  importance  under- 
estimated. These  substances  act  detrimentally,  first  of  all,  by  de- 
positing upon  the  heating-surfaces  of  the  calorizators  and  reducing 
their  efficiency.  In  case  they  get  as  far  as  the  defecation  they  are 
decomposed  by  the  lime,  forming  slimy  substances  which  to  some 
extent  contaminate  the  juice,  though  they  are  partly  precipitated 
during  carbonatation  in  such  slimy  scums  as  to  impede  filtration 
through  cloth  very  much. 

For  the  mechanical  filtration  of  diff user- juice,  pulp-  or  chip- 
eliminators  are  used,  of  which  there  are  a  great  number  of  different 
construction.  In  all  cases  the  filtration  takes  place  through  a  fine 
metal  sieve,  or  strainer,  which  is  kept  free  from  fibre  during  the 
operation  by  means  of  brushes  or  scrapers  suitably  arranged,  so 
that  the  residue  which  does  not  pass  through  the  strainer  is  readily 
removed.  These  pulp-eliminators  act  better  in  proportion  as  the 
holes  of  the  strainer  are  small,  the  filtering  surface  is  large,  and  the 
contrivance  for  removing  pulp  efficient. 

The  pulp-eliminators  must  be  arranged  in  the  juice-line, 
between  the  battery  and  the  measuring-tank,  ahead  of  the  heaters, 
so  that  the  residues  can  be  returned  conveniently  to  the  diffusers, 
and  the  juice  in  these  residues  recovered.  The  eliminators  should 
discharge  into  a  diffuser  which  is  being  freshly  filled  and  which 
is  already  half-full  of  fresh  chips  before  the  contents  of  the 
eliminators  are  added.  This  precaution  is  absolutely  essential, 


PRELIMINARY  WARMING  OF  THE  DIFFUSION-JUICE.        S3 

because  in  this  way  the  fine  chip  residues  and  fibres  are  then 
in  the  midst  of  the  good  chips  and  will  not  appreciably  hinder 
the  passage  of  the  juice,  whereas  if  they  were  allowed  to  rest 
upon  the  strainer  in  the  diffuser  they  would  stop  up  the  holes 
and  cause  bad  pressure  in  the  battery.  Even  when  the  pulp  is 
properly  mixed  into  the  cell  it  sometimes  causes  trouble.  For 
this  reason,  in  some  factories,  the  juice  is  simply  allowed  to  drain 
from  the  recovered  chips,  which  are  then  mixed  with  the  pressed 
residues.  The  slight  sugar-loss  is  held  to  be  the  lesser  of  two  evils. 
The  fact  that  albumins  are  coagulated  by  warming  the  juice, 
particularly  when  it  comes  from  the  pressed  pulp,  has  caused  the 
introduction  in  some  factories  of  the  so-called  "albumin -filters," 
through  which  the  juice  is  filtered  and  said  to  be  freed  from 
albumin  after  it  has  been  heated  to  80°  C.  (176°  F.).  The  whole 
idea,  however,  is  based  upon  error,  for  by  warming  the  juice  only 
a  very  little  albumin  separates  out,  and  in  such  a  condition  that 
it  cannot  be  removed  by  filtration.  The  total  amount  of  albumin 
in  the  diffuser-juice  amounts  to  about  0.2  to  0.3  per  cent.,  and  of 
this  only  about  10  per  cent,  (or  0.02  to  0.03  per  cent,  of  the  juice) 
can  be  coagulated.  This  amount  of  impurity  need  hardly  be 
considered,  or  at  all  events,  will  not  warrant  the  outlay  for  an 
expensive  apparatus.  It  does  no  good  to  acidify  the  crude  juice 
with  sulphurous  acid  before  heating,  because  it  curdles  the 
albumin  no  better  than  heating  alone.  Furthermore,  there  is 
no  sense  in  attempting  to  remove  this  coagulated  albumin  before 
the  defecation,  because  the  albumin  is  not  acted  upon  by  the 
lime  under  the  conditions  and  during  the  short  time  of  the 
defecation  process,  and  hence  it  goes  through  the  filter-presses  in 
an  unchanged  condition.  If,  in  spite  of  this  argument,  any  one 
believes  that  these  albumin-removers  have  proved  useful,  the 
cause  is  to  be  found  in  the  fact  that  they  have  probably  acted  as 
good  pw//>-removers.  If  these  albumin-filters  are  very  capacious, 
so  that  in  some  places  the  juice  is  not  in  contsant  motion,  it  is 
possible  for  them  to  be  the  cause  of  much  harm;  for  in  such 
cases  they  permit  certain  injurious  changes  through  the  action 
of  micro-organisms. 


84  BEET-.SUGAR   MANUFACTURE. 

The  preliminary  purification  of  the  diffuser-juice  has  also  been  at- 
tempted by  the  use  of  sulphurous  acid,  aluminium  sulphate,  baryta, 
the  electric  current  using  soluble  electrodes,  and  by  electro-dialysis. 
These  and  similar  agents  do  cause  separations  and  precipitations 
of  non-sugars  as  well  as  a  partial  decoloration.  Inasmuch  as 
nearly  all  of  these  non-sugars  are  likewise  precipitated  by  lime,  it 
seems  purposeless  to  replace  the  inexpensive  lime  by  other  dearer 
agents  which  accomplish  little  if  any  more  good;  and  even  if  they 
.are  slightly  more  efficient,  the  gain  is  not  commensurate  with  the 
increased  cost. 

The  Preliminary  Warming  of  the  Diffusion-juice. — In  the 
measuring-tanks  the  juice  from  the  diffusers  has  a  very  variable 
temperature;  the  latter  depends  upon  the  method  of  working 
.and  the  temperature  of  the  chips,  so  that  with  an  ordinary 
metliod  of  working  the  temperature  in  the  tank  may  van- 
from  0°  to  40°  C.  (32°  to  104°  F.),  but  in  most  cases  it  lies 
between  25°  and  35°  C.  (77°  to  95°  F.).  In  case  the  diffusion 
process  is  conducted  so  that  the  juice  runs  repeatedly  through 
freshly-filled  diffusers,  its  temperature  at  the  tank  may  be  as  high 
as  70°  to  80°  C.  (160°-180°  F.),  and  in  such  cases  it 'is  ready  for 
defecation  without  further  treatment.  It  is  necessary  in  most 
<}ases  to  bring  the  juice  to  the  proper  temperature  by  passing  it 
through  tubular  pre-heaters,  which  may  be  arranged  vertically  01 
horizontally,  and  sometimes  are  open  and  sometimes  closed. 

The  heating  of  the  juice  serves  at  the  same  time  to  coagulate 
those  substances  which  are  coagulated  by  heat,  thus  rendering 
them  insoluble;  in  which  condition  they  resist  the  decomposing 
action  of  the  lime  more  strongly.  The  substances  which  thus 
separate  out  are  to  some  extent  albumins,  but  chiefly  compounds 
free  from  nitrogen. 

Generally  open  pre-heaters  are  used,  because  the  tubes  can 
be  cleaned  while  they  are  in  operation.  They  have  the  dis- 
advantage of  not  being  so  efficient  and  of  having  the  surface 
of  the  juice  exposed  to  the  air.  They  become  more  efficient  if 
the  passage  of  the  juice  is  hastened  by  means  of  pumps,  or  screw 


PRELIMINARY  WARMING  OF  THE  DIFFUSION-JUICE.       85 

propellers,  and  if  fitted  with  mechanical  contrivances  for  clean- 
ing the  tubes  while  they  are  in  use. 

Closed  pre-heaters  are  preferable  to  open  ones,  and  in  these 
the  juice  is  made  to  run  quickly  through  a  series  of  tubes  arranged 
in  separate  sections.  In  such  heaters  there  is  not  so  much  precipi- 
tate adhering  to  the  heating-surface  of  the  tubes,  and  consequently 
their  action  is  quite  uniform. 

The  best  heating  arrangement  consists  of  batteries  of  separate 
single  heaters  containing  long  tubes  of  small  diameter  and  in  which 
the  juice  is  moved  at  the  rate  of  at  least  one  or  two  meters  per 
second  by  means  of  pumps.  Although  there  is  but  a  slight  deposi- 
tion upon  the  heating-tubes  when  the  Juice  is  moved  so  quickly, 
yet  it  is  necessary  to  provide  each  heater  with  suitable  valves  so 
that  it  can  be  shut  out  at  any  time  and  be  cleaned  wthout  interfering 
with  the  process  in  any  way.  The  efficiency  of  such  heaters  is  so 
much  greater  that  their  heating-surface  can  be  made  considerably 
smaller  than  in  the  open  heaters,  or  the  steam  by  which  they  are 
heated  may  be  at  a  lower  pressure. 

The  capacity  of  these  heaters  should  not  be  too  great,  because 
in  such  cases  the  juice  will  remain  too  long  in  the  heater,  and 
consequently  the  continued  heating  of  the  raw  juice  will  injure  it, 
causing,  in  particular,  a  perceptible  inversion  of  the  sugar.  An 
acid  reaction  has  no  influence  when  the  juice  is  heated  the 
normal  period,  yet  when  acid  juice  is  heated  for  some  time  at  a 
temperature  of  90°  C.  (194°  F.)  or  higher,  inversion  begins. 
To  prevent  this,  sometimes  a  little  milk  of  lime  (about  0.2 
added,  just  before  the  juice  reaches  the  heater,  in  order  to  make 
it  slightly  alkaline.  This  addition  of  lime  is  also  said  to  lessen 
the  deposition  upon  the  heating-tubes.  On  the  other  hand, 
addition  of  lime  to  the  cold  juice  is  frequently  found  to  have  an 
injurious  effect,  causing  the  juice  to  run  badly  through  the 
filter-presses.  Hence  preliminary  defecation  has  not  been  prac- 
ticed to  any  extent,  and  in  most  cases  such  treatment  is  wholly 
unnecessary. 

Most  factories  have  two  of  these  heaters,  or  two  systems  of 
heaters,  the  first  heated  by  vapor  on  its  way  to  the  condenser 


86  BEET-SUGAR  MANUFACTURE. 

from  the  last  vessel  to  the  multiple-effect  evaporator,  thus  warm- 
ing the  diffusion-liquors  to  about  45°  or  55°  C.  (113°  to  131°  F.) 
without  expense,  and  the  second  heated  by  the  vapors  from  the 
juice  in  the  first  evaporator,  bringing  the  juice  to  the  temperature 
necessary  for  defecation,  that  is,  70°  C.  (158°  F.),  or,  better  still, 
to  80°  or  85°  C.  (176°  to  185°  F.). 

Since  at  the  start  there  are  no  evaporator-vapors  for  these 
heaters  (and  this  is  true  of  other  heaters  in  the  factory),  it  is 
necessary  to  heat  them  with  direct  steam  or  else  with  the  engine- 
exhaust.  At  the  beginning  of  the  work,  when  the  juice,  apparatus, 
and  heating-tubes  are  all  cold,  special  attention  should  be  paid 
to  this  heating  of  the  juice,  for  if  this  is  not  done  the  whole 
process  suffers. 

Each  heater  must  be  arranged  so  that  it  can  be  cut  out  from 
the  juice-line  when  it  becomes  clogged  or  leaky  In  order  to  dis- 
cover any  leakage  it  is  necessary  to  examine  the  condensed  water 
regularly  for  sugar.  In  these  preheaters  there  is  more  danger 
of  loss  by  leakage  than  in  the  evaporators,  for  in  the  former  the 
pressure  is  usually  greater  within  the  tubes  than  without,  whereas 
it  is  exactly  the  opposite  in  the  evaporators. 

In  order  to  prevent  corrosion  of  the  heating-tubes  by  ammonia 
vapors,  here  as  in  the  evapora ting-apparatus,  suitable  vents  must 
be  provided. 


CHAPTER  VII. 
DEFECATION. 

THE  hot,  raw  juice  is  next  subjected  to  the  action  of  lime, 
whereby  it  is  purified,  or  defecated.  Formerly  it  was  the  almost 
universal  practice,  still  retained  in  some  factories,  to  add  milk  of 
lime  to  the  juice  and  then  immediately  saturate  the  saccharine 
solution  with  carbonic  acid.  When  this  was  done  a  large  part  of 
the  lime  was  changed  to  carbonate  before  it  had  sufficient  oppor- 
tunity to  purify  the  juice,  so  that  as  a  necessary  consequence  a 
much  larger  quantity  was  required  than  when  carbonatation  takes 
place  by  itself  and  in  separate  tanks. 

Distinction  is  made  between  milk-of-lime,  or  wet,  defecation  and 
dry  defecation.  In  both  cases  a  part  of  the  lime  is  dissolved  by 
the  juice,  while  the  greater  part  of  it  remains  suspended  and  un- 
dissolved.  The  solubility  of  lime  in  sugar-solutions  depends  upon 
the  amount  of  sugar,  the  manner  of  adding  the  lime,  and  the 
temperature.  At  ordinary  temperatures,  if  the  lime  is  in  contact 
with  the  thin  juice  for  a  length  of  time,  approximately  enough 
lime  dissolves  so  that  the  proportion  of  calcium  to  sugar  corre- 
sponds to  the  formation  of  a  monosucratc  of  calcium  in  the 
solution.  The  higher  the  temperature,  however,  the  less  lime 
dissolves,  so  that  at  the  temperature  of  80°  C.  (176°  F.),  which 
usually  prevails  during  the  defecation,  only  0.25  to  0.35  part 
of  lime  will  be  dissolved  in  100  parts  of  the  juice  containing  10 
to  12  per  cent,  of  sugar. 

The  Wet,  or  Milk-of-lime,  Defecation  is  carried  out  by  the 
addition  of  a  thick  milk  of  lime  of  about  20°  Be.  to  the  hot  raw 
juice.  The  defecators  are  provided  with  a  simple  stirring  arrange- 
ment for  mixing  quickly.  When  milk  of  lime  is  added  directly  to 

87  " 


88  BEET-SUGAR  MANUFACTURE. 

the  carbonatation-tanks  the  introduction  of  the  saturation-gas 
mixes  the  liquid. 

In  smaller  factories  milk  of  lime  is  frequently  prepared  by  slaking 
the  lime  in  flat  slaking-pans.  It  is  much  better,  however,  to 
make  use  of  slaking-drums,  similar  to  bone-black  washers,  for  in 
these  the  slaking  is  more  complete  and  without  fatiguing  labor. 
The  last  sweet  water  from  the  filter-presses  is  used  for  slaking  water. 
Where  this  is  not  available  in  sufficient  quantity,  it  is  advisable 
not  to  use  cold  spring-water,  but  rather  pure  condensed  water 
from  the  evapora ting-apparatus  or  thin  juice. 

In  order  to  remove  soluble  matter  present  in  the  lime  it  has 
been  proposed,  and  the  practice  introduced  in  some  factories,  to 
slake  the  lime  with  a  large  amount  of  water,  allow  the  liquid  to 
stand,  and  then  run  off  the  clear  supernatant  liquid  containing  the 
soluble  impurities.  Most  varieties  of  burnt  lime,  however,  contain 
scarcely  any  impurities  which  are  soluble  in  water,  and  of  such 
only  the  salts  of  the  alkalies  are  worth  considering,  for  those  con- 
stituents of  lime  which  are  difficultly  soluble  or  dissolve  very 
slowly,  such  as,  for  example,  silicate  of  lime  and  alumina,  will 
never  be  satisfactorily  removed,  for  the  simple  reason  that  they  are 
much  more  soluble  in  sugar-solutions  than  in  pure  water.  It  is 
difficult  to  see  the  advantage  to  be  gained  by  the  above  method  of 
slaking:  the  work  is  made  harder  and  the  advantage  of  using  a 
freshly  slaked  lime  is  lost.  The  longer  the  slaked  lime  stands  the 
less  energetic  becomes  its  action  upon  the  juice,  probably  because 
caustic  lime  combines  slowly  with  large  amounts  of  water.  Lime 
which  has  lain  slaked  in  the  pits  for  a  long  time  acts  slowly  and 
only  incompletely  upon  sugar- juice. 

Dry  defecation  is  done  at  the  present  time  only  by  adding 
pieces  of  burnt  lime  about  the  size  of  one's  fist  to  the  juice  at  a 
temperature  of  at  least  65°  or  70°  C.  (149°  to  158°  F.j.  Using 
powdered  lime  has  been  found  expensive,  while  this  extra  pulveriz- 
ing is  entirely  unnecessary.  Frequentty,  and  particularly  when 
the  lime-powder  is  not  added  regularly,  the  pipes  are  clogged,  the 
powdered  lime  balling  up  into  a  sticky  mass  which  distributes 
itself  slowly,  or  not  at  all,  through  the  juice.  The  defecation  then 


DEIECATIOX.  S{) 

takes  more  lime,  is  incomplete  in  its  action,  and  the  subsequent 
carbonatation  is  likewise  affected. 

When  burnt  lime  is  thrown  into  hot  juice  it  immediately  begins 
to  slake.  Since  there  is  always  a  strong  evolution  of  heat  involved 
in  the  slaking  process  (1  Ib.  of  lime  sets  free 360 heat-units,  B.T.U.), 
and  because  overheating  of  the  juice  at  one  place  is  disadvantageous, 
it  is  necessary  to  pay  particular  attention  to  the  construction  of 
the  tanks  used  for  the  dry  defecation;  this  is  especially  true  in  the 
case  of  lime  which  slakes  quickly  and  energetically. 

The  old-fashioned  method  of  dry  defecation,  by  which  a  basket 
having  perforated  sides  was  hung  in  the  juice,  should  be  discounte- 
nanced. For  a  scientific  dry  defecation  the  following  rules  should 
be  followed: 

1.  The  lime  must  come  in  contact  with  the  juice  in  a  flat 
layer. 

2.  The  juice,  and  often  the  lime  also,  must  be  constantly  kept 
in  motion. 

3.  Emptying  out  of  stones  and  other  debris  must  be  easily 
and  rapidly  effected. 

These  conditions  will  be  satisfied  if  the  lime  is  spread  out  in  the 
tanks 'upon  either  a  revolving  or  a  fixed  strainer,  while  the  juice 
is  kept  in  motion  by  means  of  a  stirrer  with  arms  both  above  and 
below  the  strainer.  The  pans  must  be  provided  with  manholes 
through  which  the  stones,  etc..  can  be  removed,  or  the  sieves 
themselves  should  be  removable. 

Dry  as  well  as  wet  defecation  can  be  made  a  continuous  process 
by  allowing  juice  to  enter  at  the  bottom  of  the  defecation-tanks 
and  to  overflow  in  the  upper  part,  thence  passing  on  to  the  carbon- 
atation, the  necessary  amount  of  lime  being  added  each  time  that 
a  measuring-tankful  flows  through  the  defecating- tanks. "  A  special 
valve  is  provided  for  emptying  pans,  being  used  when  necessary  to 
remove  stones  and  sludge,  a  more  or  less  frequent  occurrence 
according  to  the  nature  of  the  lime  employed. 

The  method  of  defecation  to  be  preferred  depends  upon  condi- 
tions having  nothing  whatever  to  do  with  the  action  of  the  lime 
itself;  for,  with  respect  to  the  purification  of  the  juice,  no  difference 
has  been  found  in  results  obtained  with  either  of  the  two  methods 


90  BEET-SUGAR  MANUFACTURE. 

when  properly  carried  out,  and  theoretically  it  is  difficult  to  see 
why  there  should  be. 

Dry  defecation  is  preferable  when  there  is  but  little  sweet 
water  from  the  presses  which  is  available  for  slaking  the  lime  and 
when  the  lime-ovens  are  in  the  vicinity  of  the  defecating- tanks,  so 
that  no  special  transportation  arrangement  is  necessary  for  bringing 
lime  to  them.  Wet  defecation,  on  the  other  hand,  is  employed  in 
factories  which  find  it  advantageous  thoroughly  to  sweeten  off 
the  filter-cake  and  where,  the  kilns  are  so  situated  that  it 
is  easier  to  pump  up  the  milk  of  lime  than  to  transport  it  in  the 
form  of  dry  lumps.  The  latter  consideration  is  not  very  impor- 
tant, however,  because  it  is  always  possible  to  place  defecating- 
tanks  near  the  lime-burners  by  pumping  or  running  the  juice  there. 

Another  point  in  favor  of  dry  defecation  is  the  fact  that  the 
action  of  the  lime  is  quicker  and  more  energetic  than  in  wet  liming, 
so  that  by  the  former  the  same  extent  of  purification  may  be 
obtained  by  use  of  a  smaller  quantity  of  lime.  Furthermore,  the 
juice  when  subjected  to  dry  defecation  retains  a  large  amount  of 
dissolved  lime  and  passes  on  somewhat  more  rapidly  to  the  car- 
bonatation-tank,  and  consequently  there  is  a  more  economical 
utilization  of  the  carbonic-acid  gas.  Finally,  it  is  questionable 
whether  it  is  wise  to  sweeten  off  the  filter-scum  very  much,  but 
when  this  is  not  done  there  is  not  enough  sweet  water  available  to 
slake  the  lime.  Hence  in  wet  defecation  it  is  necessary  to  use 
water  at  the  slaking-plant,  since  it  is  not  usually  considered  wise  to 
pump  either  crude  juice  or  the  purified  thin  juice  back  there; 
consequently,  all  other  conditions  being  equal,  factories  employing 
wet  defecation  use  up  a  little  more  coal  than  those  employing  dry 
defecation.  In  passing,  it  may  be  mentioned  that  slaking  the 
lime  warms  the  juice,  while  in  slaking  with  sweet  water  there  is  a 
slight  cooling  from  the  evaporation.  In  general,  therefore,  unless 
particular  conditions  work  to  the  contrary,  it  may  be  said  that 
dry  defecation  is  usually  preferable. 

It  should  be  mentioned  that  certain  experiments  with  dry 
defecation  have  apparently  shown  larger  losses  in  sugar  and  inferior 
purity  of  the  juice  than  when  wet  defecation  was  used.  These 


DEFECATION.  91 

experiments  are  misleading,  however,  because,  from  improperly 
carrying  out  the  dry-defecation  process,  some  insoluble  sucrate  of 
lime  was  formed  which  was  not  decomposed  by  the  carbonatation 
which  followed.  Similarly  the  disadvantage  of  producing  gray 
sugar,  often  attributed  to  dry  defecation,  is  not  in  reality  true,  for 
when  the  gray  color  appears  it  is  from  other  causes. 

Insoluble  calcium  sucrate  is  formed  in  dry  as  well  as  in  wet 
defecation,  because  the  insoluble  calcium  salts  formed  by  defecation 
have  the  property  of  carrying  down  with  them  soluble  calcium 
salts,  and  therefore  calcium  sucrate.  Insoluble  calcium  sucrate  is 
precipitated  in  small  amounts  from  all  defecated  juice  if  the  latter 
is  heated  much  after  defecation;  in  this  case  there  is  more 
precipitate  formed  after  dry  defecation,  for  the  simple  reason  that 
there  are  more  lime  salts  in  solution  than  in  the  case  of  wet  defeca- 
tion. It  is,  therefore,  necessary  carefully  to  avoid  heating  defecated 
juice  until  after  it  has  been  fully  saturated  with  carbonic-acid  gas, 
while  all  overheating  as  a  result  of  the  liquid  coming  in  contact 
with  the  hot  heating-surfaces  must  be  guarded  against.  Con- 
sequently the  temperature  of  the  ra,w  juice  should  be  high  enough 
to  make  it  unnecessary  to  heat  th?  juice  again  until  after  the 
completion  of  the  first  saturation  process. 

The  action  of  lime  upon  raw  juice  is  both  chemical  and  mechan- 
ical. Lime  acts  chemically  as  a  precipitant  and  decomposes  the  non- 
sugars  ;  the  mechanical  purification  is  due  to  the  fact  that  sus- 
pended matter  is  carried  down  with  these  precipitates.  In  raw 
juice  not  only  fibres  and  fine  particles  of  beets  which  were  not 
removed  by  the  pulp-eliminators  are  in  suspension,  but  also  all 
bodies  thrown  out  of  solution  in  warming  the  juice.  There  is  also 
in  suspension  a  certain  amount  of  micro-organisms  and  germs 
which  if  allowed  to  remain  in  the  juice  too  long  make  their  presence 
evident  in  an  unpleasant  manner  by  inverting  sugar  and  causing 
souring. 

The  slimy  precipitate  formed  by  the  lime  settles  out  readily 
at  the  bottom,  the  supernatant  juice  being  of  a  light-yellow  color, 
bright,  clear,  and  absolutely  sterile.  It  is  easy  to  make  a  separation 
such  as  the  above  with  expressed  beet- juice;  it  cannot  be  done 
with  diffusion-juice,  although  the  latter  filters  easily  when  treated 
with  sufficient  limo. 


92  BEET-SUGAR  MAMT ACTURE. 

The  chemical  action  of  lime  upon  the  non-sugars  is  accom- 
plished first  of  all  by  the  lime  neutralizing  the  free  acid  and  acid 
salts  present,  and  forming  insoluble  salts  with  a  part  of  the  organic 
acids  and  inorganic  acids,  particularly  oxalic  and  phosphoric  acids, 
all  substances  being  precipitated  which  are  insoluble  in  a  solution 
alkaline  with  lime.  The  alkalies  which  were  combined  with  the 
precipitated  acids  in  the  raw  juice,  such  as  ammonia  and  organic 
bases,  are  set  free  and  act,  together  with  the  excess  of  lime  added, 
upon  the  non-sugars.  The  alkalies,  being  the  strongest  bases, 
at  once  unite  with  those  acids  which  give  no  insoluble  compounds 
with  calcium,  to  the  extent  that  these  acids  are  present  in  the  juice, 
while  ammonia  and  the  organic  bases  remain  uncombined. 

Of  the  organic  impurities  remaining  dissolved,  many  suffer  a 
more  or  less  complete  decomposition,  particularly  invert-sugar, 
the  amides,  amines,  and  albumins.  Those  acids  yielding  solu- 
ble salts  with  lime  and  which  are,  therefore,  not  precipitated,  unite 
first  of  all  with  any  free  alkali  present,  and  finally  with  the  lime. 

Lime,  therefore,  acts  upon  the  juice  in  the  defecation  process 
as  a  purifying  agent,  the  purity  being  increased  by  the  precipitation 
of  the  non-sugars;  furthermore,  it  changes  the  nature  of  certain 
of  these  non-sugars  without  appreciably  removing  them.  Both 
actions  are  very  favorable  for  further  working  up  of  the  juice,  and 
certainty  the  latter  is  no  less  valuable  than  the  former.  In  general, 
it  may  be  said  that  the  amount  of  the  non-sugars  precipitated  is 
less  than  is  commonly  supposed.  By  defecation  and  carbonata- 
tion,  the  purity  of  the  juice  is  only  improved  from  4  to  6 
per  cent.  Of  the  12  to  15  parts  of  non-sugar  present  in  each  100 
parts  of  dry  substance  contained  in  the  raw  juice,  only  one-fourth, 
or  at  the  most  one-third,  is  precipitated,  being  30  to  50  per  cent. 
of  the  organic  matter,  30  to  40  per  cent,  of  the  nitrogenous 
matter,  and  10  to  20  per  cent,  of  the  ash.  On  the  other  hand, 
the  value  of  this  decomposing  action  of  the  lime  is  not  sufficiently 
taken  into  consideration.  By  the  decomposition  which  these 
substances  undergo  many  properties  are  lost  which  if  retained 
would  act  unfavorably  upon  subsequent  processes,  and  especially 
upon  the  crystallization  of  the  sugar. 


DEFKCATIOX.  --  93 

The  alkalies  present  in  the  raw  juice  are  not  removed  by  defi-ru- 
tion.  A  small  part  is  indeed  precipitated  with  the  lime  in  the 
carbonatation,  but  by  far  the  greater  part  remains  in  solution 
combined  with  acids  (as  carbonate  and  sulphite  after  carbon- 
atation) or  as  free  alkali,  and  is  found  again  finally  in  the 
massecuite. 

.  The  amount  of  free  alkali  present  in  the  defecated  juice  depends 
entirely  upon  the  acids  with  which  the  alkalies  were  combined  in 
the  raw  juico.  If  the  latter  contains  many  acids,  like  oxalic  acid, 
parapectic  acid,  etc.,  that  form  insoluble  compounds  with  lime 
and  the  amount  of  acid  present  after  defecation  is  insufficient  to 
unite  with  all  of  the  alkali,  a  considerable  amount  of  the  latter 
remains  free,  which  during  the  defecation  and  in  the  subsequent 
operations  decomposes  the  non-sugars.  In  such  juices,  which 
therefore  contain  carbonates  of  the  alkalies  after  carbonatation, 
i\  decrease  in  alkalinity  during  evaporation  acts  in  no  way 
detrimentally.  Lime  salts  arc  not  "present,  or  at  least  only  in 
traces.  If  the  diffusion  is  good  with  a  thorough  lixiviation  the 
amount  of  alkalies  and  their  salts  increase,  as  soluble  alkaline  pec- 
t mates  are  dissolved,  while  the  lime  salts  generally  decrea.se 
somewhat. 

If,  on  the  other  hand,  the  acids  originally  combined  with  the 
alkalies  form  only  soluble  salts  with  lime,  they  unite  with  the 
alkalies  set  free  in  the  defecation  process,  replacing  the  lime  in 
these  salts  either  during  defecation  or  subsequently  in  carbonation. 
Free  alkali  or  alkaline  carbonates  are  not  present  at  all  in  such 
juices,  and  the  alkalinity  which  must  finally  be  retained  by  them 
is  occasioned  not  by  the  true  alkalies  but  by  ammonia,  organic 
bases,  or  free  lime.  If  the  decomposition  of  the  invert-sugar, 
amides,  albumins,  etc.,  be  not  completed  by  defecating  juices  of 
this  nature,  later  on  the  juice  may  react  neutral  or  even  acid.  To 
avoid  this  the  saturation  (carbonatation)  of  the  thin  juice  in  such 
cases  must  not  be  carried  so  far  as  to  remove  free  lime  completely, 
for  the  decomposition  is  effected  in  the  desired  way  during  the 
subsequent  operations  and  the  lime  eventually  unites  with  the 
acids  set  free.  Such  juices  are,  therefore,  always  rich  in  lime  salts. 

As  far  as  can  be  done,  all  possible  decomposition  of  the  non- 


94  BEET-SUGAR  MANUFACTURE. 

sugars  by  lime  should  take  place  during  defecation.  It  is  entirely 
impossible,  however,  to  complete  this  decomposition  at  this  latter 
stage,  because  some  of  these  substances,  chiefly  the  amides  and 
bodies  similar  to  the  albumins,  decompose  altogether  too  slowly 
under  the  conditions  prevailing  at  this  point,  also  because  it  is  not 
advisable,  and  indeed  dangerous,  to  lengthen  out  the  defecation 
too  much,  or  to  maintain  a  high  temperature,  unless  one  wishes  to 
risk  redissolving  certain  of  the  precipitated  non-sugars.  Further- 
more, the  conditions  prevailing  during  the  evaporation  are  so 
favorable  for  the  completion  of  these  decompositions,  as  will  be 
shown  later  on,  that  it  would  be  bad  practice  to  carry  out  the 
defecation  in  any  other  way  than  that  giving  proper  precipitation 
of  the  insoluble  matter  and  consequent  easy  carbonatation. 

With  regard  to  the  most  favorable  temperature  for  defecation, 
experience  has  shown  this  to  be  between  70°  and  80°  C.  (158°-176° 
F.)  for  normal  beets. 

Cold  defecation  has  been  tried  and  recommended  on  the  assump* 
tion  that  lime  at  high  temperatures  decomposes  a  portion  of  the 
precipitated  substances,  bringing  them  into  solution  again.  How- 
ever, proof  of  this  assumption  is  lacking;  many  experiments,  on 
the  contrary,  showing  that  there  is  practically  no  difference  between 
hot  and  cold  defecated  juice  in  case  the  latter  is  heated  after  it 
comes  from  the  filter-presses,  and  as  long  as  the  action  of  the  lime 
takes  place  within  the  limits  employed  in  practice.  Cold  defecation 
should  not  be  introduced  into  the  industry,  because  the  scums 
cannot  be  filtered  quickly  enough  even  when  infusorial  earth  or 
a  similar  substance  is  added. 

Temperatures  above  90°  C.  (194°  F.),or  even  the  boiling-tem- 
perature, are  not  to  be  advised  for  defecation.  Only  when  beets 
are  of  bad  quality  and  contain  considerable  invert-sugar  and  other 
substances  decomposable  by  lime,  do  high  temperatures  exert  a 
favorable  effect,  although  even  then  long  boiling,  or  even  boiling 
at  all,  should  be  avoided,  because  it  is  likely  to  cause  precipitated 
substances  to  redissolve.  The  opinion  that  defecated  juice  which 
has  been  boiled  up  yields  scums  which  can  be  more  readily  filtered 
off  is  not  confirmed;  on  the  other  hand  it  is  difficult  to  saturate 
boiling-hot  juice  with  gas  and  the  scums  hold  back  sugar. 


DEFECATION.  95 

The  duration  of  the  defecation  must  be  kept  within  certain 
definite  limits.  At  the  relatively  low  temperatures  of  from  70°  to 
80°  C.  (158°  to  176°  F.)  about  fifteen  minutes  is  the  proper  length 
of  time,  while  at  higher  temperatures  five  to  ten  minutes  is 
sufficient. 

The  amount  of  lime  deemed  necessary  in  different  factories 
varies  between  wide  limits.  For  neutralization  of  raw-beet  juice 
and  precipitation  of  those  substances  which  lime  will  throw  down, 
only  about  0.15  to  0.20  per  cent,  of  lime,  reckoned  upon  the 
amount  of  juice,  is  necessary.  True  defecation,  that  is,  one  in 
which  the  scums  are  readily  deposited,  leaving  a  clear  supernatant 
juice,  is  obtained  by  adding  from  J  to  f  per  cent,  of  lime,  but 
with  this  amount  it  is  not  possible  satisfactorily  to  complete  the 
process,  since  the  sludge  thus  obtained  will  filter  very  slowly. 
A  juice  which  will  filter  satisfactorily  is  obtained  by  the  addition 
of  from  1J  to  2  per  cent,  of  lime. 

The  addition  of  a  small  amount  of  "  Kieselguhr  "  (diatomace- 
ous  earth)  before  defecation  assists  the  precipitation  of  the 
albumins,  so  that  only  about  1  per  ce»t.  of  lime  is  necessary  for 
obtaining  a  juice  that  filters  easily.  Apparently  the  kieselguhr 
acts  mechanically  only,  making  the  scums  more  porous,  just  as 
do  other  absorbent  materials,  such  as  brick  dust,  which  also 
economize  the  amount  of  lime  necessary  for  defecation,  when  the 
beets  are  of  good  quality.  Whether  such  addition  pays  depends 
on  the  cost  of  the  material  compared  with  that  of  the  lime  saved. 

However,  in  many  factories  where  this  amount  is  accepted 
as  a  minimum,  it  is  not  considered  adequate  and  2-V  to  3  per  cent, 
or  more  lime  is  added  with  the  feeling  that  in  this  way  a  better 
purification  of  the  juice  is  obtained.  It  is  certainly  true  that 
where  larger  amounts  of  lime  are  employed  juices  of  lighter 
color  are  obtained  which  also  contain  less  dissolved  calcium 
salts;  but  with  regard  to  the  actual  purity  of  the  juice,  up 
to  the  present  time  there  has  been  found  to  be  no  perceptible 
influence  in  the  use  of  a  smaller  or  larger  quantity  of  lime. 
Moreover,  the  decomposition  of  the  substances  which  are  acted 
upon  by  the  lime  does  not  take  place  more  rapidly  or  ener- 
getically when  an  excess  of  lime  is  employed  because  only  the 


96  BEET-SUGAR   MANUFACTURE. 

•v 

lime  that  is  in  solution  is  active;  the  amount  of  lime  dissolved 
depends  solely  upon  the  sugar-content  and  the  temperature,  and 
not  at  all.  upon  the  quantity  added.  For  this  reason  the  more  or 
less  favorable  action  resulting  from  the  use  of  considerable  lime 
is  shown  not  during  the  defecation,  but  afterwards,  in  the  carbon- 
atation.  Whether  the  advantages  which  result  there  are  sufficient 
to  counterbalance  the  numerous  bad  effects  arising  from  use  of  too 
much  lime  must  be  figured  out  for  each  particular  case.  Use  of 
large  amounts  of  lime  occasions  not  only  additional  expense  in 
providing  lime  and  carbonic  acid,  but  also  causes  an  increased 
amount  of  scum  and  greater  losses  of  sugar  retained  by  them, 
making  more  filter-presses  and  a  larger  lime-kiln  necessary.  If  it 
be  desired  to  manufacture  a  particularly  clear  juice,  as  is  the  case 
with  factories  making  the  finer  grades  of  sugar,  then  the  use  of  a 
relatively  large  amount  of  lime  seems  justifiable,  but  hardly  in 
those  factories  making  ordinary  sugar.  In  working  up  a  partic- 
ularly bad  lot  of  beets  it  sometimes  seems  better  to  lime  strongly 
in  order  to  improve  the  working  of  the  filter-presses. 

The  amount  of  milk  of  lime  to  be  added  to  the  raw  juice  is 
measured  off  in  ordinary  or  automatic  measuring- tanks.  It  is 
highly  desirable  that  the  density  of  the  milk  of  lime  should  be 
uniform,  and  that  of  20°  Baume  has  proved  most  suitable,  for 
otherwise  there  is  likely  to  be  variation  in  the  amounts  of  lime 
added  to  the  juice.  In  the  case  of  dry  defecation  the  lime  should 
be  broken  up  into  lumps  of  as  nearly  the  same  size  as  possible, 
which  may  be  either  weighed  out  or  measured.  While  it  would 
seem  as  if  weighing  out  of  the  lime  would  be  more  accurate,  as  a 
matter  of  fact  measuring  is  preferable,  as  in  this  case  the  influence 
of  badly  burnt  and  consequently  heavier  lime  is  not  so  serious. 

Lime  should  be  used  fresh,  or  as  soon  after  it  has  been  burnt 
as  possible,  as  it  then  slakes  most  rapidly.  Crumbling  which  takes 
place  on  long  standing  is  caused  by  formation  of  calcium  hydroxide 
and  carbonate  from  contact  with  moisture  and  carbonic  acid  in  the 
atmosphere.  It  will  be  found  necessary  to  use  larger  amounts  of 
such  lime.  It  is  best  to  remove  fuel-ash  as  completely  as  possible 
from  lime  which  has  been  in  direct  contact  with  the  fuel  in  the  kiln, 
to  avoid  contaminating  the  juice. 


CHAPTER  VIII. 
CARBONATATION. 

Carbon  dioxide,  taken  from  the  lime-kilns,  is  the  reagent  used 
for  precipitating  lime  in  the  defecated  juices. 

Formerly  there  was  a  wide-spread  fear  that  carbonic  acid  in 
contact  with  the  scums  would  act  as  a  solvent  of  the  precipitated 
matter,  based  on  the  fact  that  a  blackening  of  the  juice  and  scums 
occurred  in  supersaturated  liquors;  that  is,  in  liquors  which  were 
treated  with  carbonic  acid  till  neutral  or  even  slightly  acid.  Hence 
those  processes  were  recommended  in  which  carbonatation  was 
made  in  the  clear  filtered  liquors  after  the  precipitated  matter  had 
been  removed  by  filtration.  Such  procedure  is,  however,  based 
on  incorrect  reasoning,  as  will  be  made  clear  later. 

It  is  almost  the  universal  practice  now  to  make  the  carbonatation 
on  the  juice  while  still  mixed  with  defecated  matter  and  undissolved 
lime.  The  defecated  juice  accordingly  goes  to  the  carbonatation- 
tank,  which  may  also  serve  for  the  defecator  itself,  where  direct 
carbonatation  of  defecated  juices  is  practiced. 

Carbonatation-tanks  are  open  or  closed,  round  or  rectangular r 
and  usually  of  considerable  depth.  In  the  bottom  there  are 
devices  for  distributing  the  saturation-gas,  as  well  as  heating-coils 
or  steam-injectors. 

The  simplest  and  most  generally  used  distributing  devices  for 
carbonatation-gas  are  perforated  pipes.  They  distribute  the  gas 
exceedingly  well,  but  have  the  disadvantage  that  in  ordinary  con- 
ditions of  carbonatation  the  holes  become  easily  clogged,  especially 
if  they  are  small.  Since  the  task  of  boring  out  these  hoies  is  dis- 
agreeable and  dangerous  for  workmen,  arrangements  have  been 

97 


98  BEET-SUGAR  MANUFACTURE. 

devised,  particularly  for  the  rectangular  pans,  to  lift  out  these 
pipes  and  replace  them.  To  do  away  entirely  with  the  labor  of 
this  cleaning,  distributing-boxes  are  sometimes  used,  open  at  the 
bottom,  with  the  lower  edges  notched  to  facilitate  the  division  of 
the  gas,  usually  the  sides  also  being  perforated.  Another  arrange- 
ment which  has  been  well  recommended  consists  of  piping  with 
transverse  slits  on  the  under  side  which  are  always  kept  open 
by  revolving  scrapers. 

The  absorption  of  the  carbonic  dioxide  from  the  satu- 
ration-gas depends  not  only  on  the  size  of  the  gas  bubbles, 
but  on  the  depth  of  liquor  through  which  the  gas  passes  and 
especially  on  the  alkalinity.  For  more  intimate  mixture  of  gas 
and  juice,  turbines  and  stirrers  on  the  principle  of  injectors,  as 
well  as  paddles  which  keep  the  juice  in  motion  and  divide  up  the 
bubbles,  have  proved  efficient  in  practice.  Experience  has  not 
yet  shown  that  such  devices  made  notable  improvement  in  the 
process.  With  all  such  gas-distributors,  the  amount  of  absorp- 
tion and  consequent  speed  of  saturation  depends  on  the  alkalinity 
of  the  juice.  The  absorption  of  carbon  dioxide  down  to  an 
alkalinity  of  0.15  to  0.18  does  not  vary  much,  but  below  that 
point  it  falls  off  in  quite  rapidly  increasing  ratio.  This  is  well 
shown  in  the  continuous  carbonatation  process  shortly  to  be 
described;  in  the  first  tank,  where  the  alkalinity  was  0.15  to  0.20 
in  one  instance,  50  to  70  per  cent,  of  the  carbon  dioxide  intro- 
duced was  utilized,  while  in  the  second  tank,  where  the  alkalinity 
was  0.08  to  0.10,  only  50  to  55  per  cent,  was  utilized.  The 
second  carbonatation,  with  an  alkalinity  of  0.04  to  0.05,  utilized 
45  to  50  per  cent. 

Evidently  a  considerable  proportion  of  the  carbon  dioxide  is 
lost.  A  suggestion  has  been  made  to  atomize  the  juice  into  the 
kiln-gases  so  as  to  better  economize  the  carbon  dioxide,  but  this 
idea,  which  is  in  itself  good,  has  never  been  put  in  practice,  since 
the  juice-atomizer  would  clog  up.  It  is  feasible,  however,  to 
again  utilize  the  gases  escaping  from  the  tank,  which  still  hold  12 
to  15  per  cent,  or  more  of  carbon  dioxide,  sucking  them  out  by  a 
pump  or  steam  siphon  and  forcing  them  through  the  juice,  a  sepa- 
rate tank  of  course  being  necessary.  As  a  rule  there  is  no  neces- 


CARBONATATION. 

sity  of  better  economy  in  the  use  of  the  carbon  dioxide,  for  every 
factory  which  burns  its  own  lime  always  has  an  excess  of  gas. 

The  temperature  of  the  gas  has  little  influence  on  its  absorp- 
tion; it  appears  that  higher  temperatures  arc  more  favorable. 

The  temperature  of  the  juice  falls  during  carbonatation, 
partly  because  steam  is  carried  off  by  the  escaping  gas,  and 
partly  because  the  gases  themselves  absorb  heat.  This  heat 
loss  is  made  up  to  some  extent  by  the  heat  of  formation  of 
calcium  carbonate  from  the  hydrate,  being  330  heat-units  (calories) 
for  every  kilogram  of  calcium  oxide  (1  Ib.  =594  B.T.U.)-  This 
heat  loss  is  greater  in  proportion  to  the  temperature  of  the  juice 
and  the  poorer  the  gases  are  in  carbon  dioxide  and  the  more  lime 
there  is  to  saturate,  since  more  gas  must  be  passed  through. 
Usually,  the  temperature  drop  of  the  juice  can  be  taken  as  5°-6° 
C.  (9°-14°  F.),  when  the  lining  is  2  per  cent.,  the  juice  tem- 
perature 80°  C.  (176°  F.),  and  the  carbon-dioxide  content  of  the 
gases  25-30  per  cent. 

Steam-coils  are  not  suited  for  heating  defecated  juices  in 
carbonatation-tanks,  as  they  tend  to  become  quickly  covered 
with  scale  and  thus  inefficient.  This  scaling  is  not  usually  a 
result  of  the  routine  of  the  saturation  process,  but  of  the  inter- 
ruptions of  the  work,  and  this  is  also  true  of  the  clogging  of 
the  gas-distributors.  When  a  tank  is  emptied  for  shutting  down, 
some  scum  always  remains  on  the  coils  or  in  the  holes  of  the 
gas-distributors.  It  dries  there  or  burns  on,  and  thus  forms  a 
thick  scale  in  such  places.  If  it  be  necessary  to  heat  up  the 
juice  in  these  tanks,  steam-injectors  should  be  used.  Usually 
heating  of  juices  before  carbonatation  is  to  be  avoided,  as  already 
pointed  out,  while,  on  the  other  hand,  bringing  the  completely 
saturated  liquors  to  high  temperature  is  decidedly  advantageous. 
In  order  to  prevent  dilution,  which  would  result  from  heating 
with  steam -injectors,  and  likewise  to  utilize  the  low-cost  steam 
from  the  evaporators,  it  is  advisable  to  pump  the  juice  out  of 
the  tank  through  a  closed  tubular  heater  which  has  a  temperature 
of  at  least  100°  C.  Xo  scale  on  the  tubes  is  to  be  feared  if  the 
defecated  juice  enters  the  heater  from  above  and  goes  out  at 


100  BEET-SUGAR   MANUFACTURE. 

the  bottom,  and  provided  the  heater  is  always  kept  full  while  in 
in  use. 

As  stated  above,  the  depth  cf  liquor  in  the  tank  must  be 
as  great  as  possible  to  utilize  the  carbon  dioxide  most  efficiently, 
but  obviously  not  so  great  as  to  prevent  the  gas-pump  from  over- 
coming the  back  pressure.  Likewise  the  sides  of  the  tank  should 
extend  above  the  liquor-level  to  a  considerable  height,  at  least 
3  meters  (10  feet),  better,  4-5  meters  (13-16  feet),  so  that 
there  will  be  sufficient  room  for  foam  formed  during  the  satura- 
tion process. 

High  sides  to  the  tank,  giving  plenty  of  space,  afford  the  best 
way  to  prevent  foaming  over;  the  more  the  air-space  the  less 
necessary  becomes  other  preventives,  such  as  foam-preventers  and 
application  of  grease.  Foam-preventers  use  considerable  direct 
.steam  and  dilute  the  juice.  The  use  of  grease  and  oils  likewise 
costs  some  money,  not  to  mention  the  fact  that  it  puts  undesirable 
impurities  in  the  juice,  or  may  be  the  cause  of  trouble  in  the 
scum-presses,  unsaponifiable  oils  in  particular  being  causes  of  bad 
nitration.  Nevertheless  the  use  of  a  small  quantity  of  oil  or 
grease  cannot  always  be  avoided.  In  such  cases  choose  those  of 
greatest  viscosity,  such  as  tallow  or  castor-oil,  because  a  very 
small  quantity  of  these  will  do  and  devices  to  control  the  amount 
added  can  be  made  of  convenient  size.  A  useful  contrivance 
is  a  large  cask  with  a  gauge-glass  from  which  the  oil  can  be 
pumped  or  forced  over  to  the  tank  through  piping.  Pressure 
can  be  conveniently  obtained  by  a  connection  from  the  gas-pump. 

The  spent  gases  from  the  carbonatation-tanks  are  removed  by 
an  exit-pipe  of  large  diameter  which  allows  any  entrained  foam 
to  drop  back.  Sometimes  there  is  an  enlarged  section  in  this 
pipe  which  acts  as  a  juice-trap.  If  every  tank  is  not  equipped 
with  its  special  exit-flue  leading  to  the  open  air,  that  is,  when 
there  is  only  one  common  exit-pipe  for  several  tanks,  care  should 
be  taken  to  have  devices  to  prevent  foam  from  one  pan  getting 
into  another,  for  unsaturated  juice  getting  into  a  tank  in  which 
saturation  is  complete  would  make  the  scums  filter  badly  and 
slime  up  the  filter-presses. 


CARBOXATATIOX.  101 

The  best  way  is  to  have  the  exit-pipes  from  each  tank  lead  up 
into  a  common  collecting-pipe  from  which  the  entrained  juice  runs 
down  into  some  tank  which  has  recently  been  filled.  A  gas-collector 
is  placed  in  this  exit-pipe  so  that  tests  can  be  made  of  the  contents 
of  carbon  dioxide  in  the  escaping  gases. 

Almost  universally  the  saturation-gas  is  forced  into  the  juice 
by  pumps.  These  pumps  are  not  power-driven,  but  are  always 
equipped  with  independent  steam-cylinders,  so  that  the  stroke 
can  be  regulated  according  to  the  demand  for  carbon  dioxide. 
There  is  little  to  recommend  in  steam-injectors,  which  were  used 
for  a  time,  since  they  require  a  large  amount  of  steam,  heat  up  and 
dilute  the  juice  excessively,  and  cannot  overcome  any  considerable 
back  pressure.  As  auxiliaries  to  help  out  during  pump  repairs 

they  are  useful. 

The  carbonatation  cf  the  defecated  juice  requires  the  greatest 
attention  on  the  part  of  the  workman  in  charge,  for  a  poorly  con- 
ducted or  slow  saturation  injures  the  juice  and  makes  great  trouble 
in  the  filter-presses  later.  The  duties  of  the  man  in  charge  of  the 
carbonatation  are  just  as  responsible,  therefore,  as  those  of  the 
batteryman,  especially  if  the  original  quality  of  the  juice  is  bad. 
Where  the  defecation-plant  is  independent  the  man  in  charge  of 
the  saturation  must  often  ascertain  whether  the  juice  is  properly 
defecated  before  applying  the  gas.  The  spoon  tests  should  show 
a  deposit  readily  separating  and  leaving  the  supernatant  juice 
clear.  In  the  dry-defecation  process  the  filtrate  should  show  an 
alkalinity  of  0.25-0.35,  according  to  the  temperature  of  the  juice; 
in  defecation  with  milk  of  lime,  somewhat  less. 

As  soon  as  the  carbonatation- tank  is  filled  to  the  proper  depth 
the  gas-valve  is  opened,  only  a  little  at  first,  because  in  the  be- 
ginning the  juice  foams  badly.  Since,  however,  the  pump  is  working 
continuously,  in  order  to  better  utilize  the  gas,  not  only  the  valve 
to  one  tank  is  opened,  but  to  two  or  three  tanks,  and  in  such  a  way 
that  the  most  saturated  tank  whose  juice  foams  the  least  gets  the 
most  gas,  and  the  others  less  accordingly.  For  this  procedure  it 
i-  m-res.ary  to  ke^p  all  the  tanks  equally  filled  with  juice.  If 
it  were  not  so,  the  heavier  (low  of  gas  would  be  into  the  least  filled 


102  BEET-SUGAR  MANUFACTURE. 

tanks  in  spite  of  the  partially  closed  valves,  since  the  back  pressure 
would  be  less,  and  hence  these  tanks  would  be  completely  saturated 
before  the  others  although  the  latter  might  have  stood  longer. 
Systematic  supervision  and  regulation  of  the  carbonatation  process 
wrould  thus  be  impossible. 

The  man  in  charge  takes  frequent  spoon  tests  during  the  conduct 
of  the  saturation  and  observes  the  separation  of  the  precipitate. 
In  open  tanks  the  tests  are  taken  with  a  long-handled  spoon  or 
with  a  small  syringe;  in  closed  pans  where  the  workman  stands 
under  the  pan  the  test  is  taken  from  a  cock.  Well- trained  workmen 
can  make  quite  satisfactory  saturations  by  following  this  test; 
in  many  factories  workmen  go  by  other  signs,  as,  for  instance,  the 
sound  made  by  the  gas-bubbles. 

The  behavior  of  the  juice  in  the  carbonatation  process,  as  far  as 
outward  appearances  go,  is  as  follows:  As  soon  as  the  gas  begins 
to  flow  the  defecated  juice  begins  to  thicken  in  proportion  to 
its  sugar-content;  raw  juice,  however,  not  thickening  perceptibly. 
The  spoon  test  shows  a  gelatinous  precipitate  no  longer  separating 
out.  The  result  of  this  gelatinous  condition  is  the  heavy  foam 
already  mentioned  as  occurring  at  the  beginning  of  saturation,  and 
there  is  a  loud  noise  made  by  the  passage  of  the  gas.  Filtration 
of  the  juice  at  this  stage  is  quite  impossible;  if  this  juice  by  chance 
or  carelessness  gets  to  the  scum-presses,  the  cloths  are  immediately 
slimed  up.  As  more  gas  is  passed  in,  the  gelatinous  state  of  the 
juice  entirely  disappears,  the  gas  enters  more  evenly  and  in  smaller 
and  smaller  bubbles  as  the  juice  becomes  more  fluid,  the  foaming 
ceases  entirely,  and  finally  a  juice  is  obtained  out  of  which  the 
precipitate  again  subsides  readily  and  quickly  and  is  easily  removed 
by  filtration. 

During  this  saturation  the  alkalinity  obviously  diminishes,  but 
not  with  any  regularity.  In  the  beginning  it  diminishes  quite 
quickly,  from  0.25-0.35  to  about  0.15-0.18.  At  this  point  it  remains 
almost  unchanged,  because  now  about  the  same  amount  of  lime  re- 
dissolves  as  is  precipitated  by  the  carbonic  acid.  When  all  of  the 
lime  has  been  acted  upon,  the  alkalinity  sinks  rapidly  to  0.06-0.10; 
hence  this  value  determines  the  completion  of  the  first  saturation, 


CARBONATATION.  1 OS 

being  the  stage  when  the  juice  is  in  best  condition  and  easily 
filtered.  Just  at  the  completion  of  the  carbonatation  the  man  in 
charge  must  take  great  care  not  to  oversaturate  the  juice. 

In  every  house  where  special  dependence  is  put  on  the  chemical 
control,  titrations  are  made  from  every  tank  at  completion  of  the 
saturation,  to  make  sure  that  juice  of  proper  and  uniform  alkalinity 
is  sent  to  the  filter-presses,  the  spoon  test  being  used  merely  for 
a  rough  preliminary  determination  of  the  saturation-point.  The 
most  desirable  final  alkalinity  value  varies,  according  to  the  con- 
dition and  composition  of  the  juice,  between  0.06-0.10  per  cent,  of 
lime,  with  phenolphthalein  used  as  an  indicator,  or  0.09-0.12  per 
cent.,  using  rosolic  acid. 

The  chemical  reactions  in  the  carbonatation  process  are  not 
yet  fully  explained.  By  the  introduction  of  carbonic  acid,  not  only 
calcium  carbonate  is  formed,  but  also  a  double  salt  of  calcium 
carbonate,  calcium  sucrate,  and  possibly  caustic  lime.  This 
latter  compound  forms  the  gelatinous  precipitate  which  contains 
considerable  sugar  in  the  form  of  lime  sucrates.  This  is  more 
copious  and  thickens  the  juice  more,  the  colder  the  carbonatation 
is  carried  out  and  the  greater  the  suga'r-content ;  although  other 
conditions,  as  yet  unknown,  have  marked  influence  on  the  amount 
and  constitution  of  these  compounds. 

These  compounds  are  partially  decomposed  by  the  heat  and 
dilution,  further  treatment  with  carbonic  acid  breaking  them  up 
completely.  As  the  saturation  progresses,  the  amount  of  double 
salts  which  were  first  formed  continually  diminishes,  and  finally, 
if  the  alkalinity  is  brought  down  to  the  proper  limit,  they  usually 
disappear.  In  many  cases,  however,  this  decomposition  is  incom- 
plete, so  that  small  quantities  of  these  double  compounds  remain 
in  the  scum  and  cause  increased  sugar-loss. 

Aside  from  those  reactions  of  the  carbonatation  process  which 
are  necessarily  connected  with  the  neutralization  of  the  lime,  there 
are  other  side  reactions,  some  favorable,  some  objectionable.  A 
favorable  reaction  is  the  precipitation,  along  with  the  calcium 
carbonate,  if  only  to  a  slight  extent,  of  those  lime  salts  soluble  in 
the  alkaline  juice.  This  precipitation  also  can  only  be  attributed 


104  BEET-SUGAR  MANUFACTURE. 

to  the  formation  of  double  salts,  and  in  fact  more  lime  salts  will 
be  carried  down  in  proportion  as  more  lime  was  used  in  defecation. 

Another  consequence  of  saturation  is  the  coagulation  of  the 
soft,  slimy,  flocculent,  organic  or  inorganic  precipitates  previously 
formed  in  the  defecation  which  separate  out  with  the  calcium 
carbonate.  The  separation  of  the  calcium  carbonate  does  not 
take  place  immediately  by  itself,  but  requires  time,  although  the 
period  is  brief.  The  precipitate  forms  more  readily  and  quickly 
if  minute  particles  are  present  for  it  to  collect  on,  and  the  little 
particles  of  slime  in  the  juice  answer  this  purpose.  These  light 
particles,  which  by  themselves  would  filter  out  only  slowly  and 
poorly,  become  surrounded  wholly  or  in  part  with  an  envelope  of 
calcium  carbonate,  and  thereby  lose,  to  a  greater  or  lesser  degree, 
their  slimy  or  gelatinous  nature  and  so  can  be  filtered  off  much 
more  easily.  Therefore,  carbonatated  juices  always  filter  bet- 
ter than  those  only  defecated,  even  if  these  latter  are  mixed 
with  calcium  carbonate,  infusorial  earth,  etc.,  because  such  mixing 
cannot  effect  the  coagulation  which  results  from  the  saturation. 

There  is  an  unfavorable  reaction  which  occurs  at  times  during 
the  course  of  the  carbonatation  and  causes  an  appreciable  amount 
of  sugar  to  be  retained  by  the  scums  even  when  the  process  is 
completed  under  normal  conditions. 

The  amount  of  insoluble  lime  sucrate  retained  by  the  precipitate, 
or  scums,  is  usually  dependent  upon  the  following:  (1)  lime  sucrate 
is  deposited  during  defection  due  to  local  overheating  of  the 
juice  or  from  too  much  heat  after  the  lime  is  added;  (2)  a  por- 
tion of  the  lime  sucrate  which  is  in  the  form  of  double  compounds 
at  the  beginning  of  the  saturation  remains  undissolved  at  the 
end  of  the  process;  (3)  lime  sucrate  is  thrown  out  with  the 
other  insoluble  lime  salts,  precipitated  either  by  defecation  or 
carbonatation.  The  amount  of  lime  sucrate  which  separates 
out  and  remains  in  the  scums  is  usually  exceedingly  small,  but 
under  unfavorable  conditions,  as  when  the  three  causes  above 
enumerated  act  together,  it  may  become  significant.  The  result 
of  such  sucrate  precipitation  is  a  high  sugar-content  of  filter- 
press  cake,  which  can  only  be  lowered  by  a  tedious  sweetening  off, 


CAKBONATATION.  105 

and  a  lowering  of  the  purity  of  the  juice,  for  by  insufficient 
sweetening  off  there  is  less  sugar  for  an  equal  amount  of  non- 
sugar,  while  if  the  sweetening  off  is  prolonged,  proportionally 
more  non-sugar  is  dissolved  out  of  the  cake. 

If  the  amount  of  sucrates  precipitated  is  excessive,  and  if, 
therefore,  the  filter-cake  does  not  permit  a  ready  sweetening  off, 
one  should  try  to  remedy  the  evil  by  reducing  the  alkalinity  as  far 
as  practicable;  but  since  the  insoluble  sucrate  will  surely  be  decom- 
posed in  juices  free  from  caustic  lime,  it  is  advisable  to  oversaturate 
the  defecated  juice  if  the  scums  from  the  filter-presses  do  not 
sweeten  off  easily,  which  means  that  not  only  the  lime  alkalinity 
is  partly  or  wholly  removed,  but  also  any  free  alkali.  Juice  and 
scums  then  have  a  dark,  almost  black,  objectionable  color.  The 
scums  no  longer  settle  well  and  the  supernatant  juice  is  turbid. 
Such  an  oversaturated  juice  will,  therefore,  not  filter  in  this  condi- 
tion. If,  however,  some  milk  of  lime,  or  freshly  defecated  juice, 
is  mixed  with  this  oversaturated  liquor,  so  that  the  alkalinity  rises 
to  at  least  0.10,  the  mixture  becomes,  as  far  as  external  behavior 
goes,  identical  with  saturated  juice  of  the,  same  alkalinity. 

Oversaturation  without  doubt  makes  a  worse  juice,  for  the 
action  of  the  carbonic  acid  on  juices  free  from  caustic  lime,  or 
even  entirely  neutral  or  weakly  acid,  is  to  redissolve  organic  non- 
sugars  as  well  as  precipitated  lime  salts  and  coloring  matters. 
Whether  by  the  mixture  of  supersaturated  juice  with  milk  of  lime 
or  defecated  juice  all  dissolved  non-sugars  are  again  precipitated 
is  unknown.  Apparently  they  are,  since  in  practice  no  difference 
can  be  detected  in  the  behavior  of  such  juice  from  that  of  juice 
saturated  according  to  the  correct  procedure,  providing  the  juice  is 
not  tao  much  oversaturated  and  if,  finally,  enough  lime  is  again 
added  to  make  the  mixture  show  more  than  0.10  alkalinity,  and 
a  subsequent  short  additional  saturation. 

The  saturation  as  ordinarily  conducted,  namely,  that  of  treating 
each  tank  by  itself,  has  now  been  described.  Since  a  continuous 
process  always  has  certain  advantages,  in  past  years  many  experi- 
ments have  been  tried  in  this  direction.  These  experiments,  which 
were  attempts  to  produce  a  continuous  carbonatation  by  means  of 


106  BEET-SUGAR   MANUFACTURE. 

forcing  the  defecated  juice,  mixed  with  the  saturation-gas,  through 
curved  pipes  in  order  better  to  utilize  the  carbonic  acid  by  an  im- 
mediate and  intimate  mixture  of  juice  and  gas,  have  failed  owing 
to  the  impossibility  of  maintaining  a  uniform  alkalinity;  sometimes 
the  juice  would  come  out  from  the  exit-pipe  undersaturated,  some- 
times oversaturated.  It  is  clear  that  for  the  maintenance  of  con- 
stant alkalinity  varying  proportions  of  juice  must  be  continually 
taken  in  actual  practice,  since  the  amount  of  carbonic  dioxide  in  the 
saturation-gas,  as  well  as  the  quantity  of  lime  in  the  juice,  changes 
to  a  marked  degree.  Therefore,  best  results  are  obtained  by  a 
continuous  process  of  the  simplest  description:  treating  the 
defecated  juice  in  an  ordinary  carbonatation-tank  fitted  with 
a  good  gas-distributing  apparatus  and  introducing  at  the  same 
time  the  appropriate  amount  of  gas.  Since  the  saturation-gas 
flows  in  continuously,  perforated  tubes  can  be  used  for  distribu- 
tors, for  under  these  conditions  the  holes  will  not  stop  up  easily. 
A  convenient  distributing-apparatus  consists  of  a  horizontal  cross  of 
piping,  the  arms  of  which  are  perforated  all  on  the  same  side.  The 
gas  as  it  blows  in  rotates  the  contents  of  the  tank,  producing  an 
excellent  distribution  of  the  bubbles  and  a  high  economy  of 
carbonic  acid.  From  this  first  tank  the  almost  completely  saturated 
juice  goes  up  through  a  pipe  out  from  the  top  into  the  bottom  of 
a  second  tank,  in  which  it  is  again  treated  with  sufficient  carbon 
dioxide  to  give  the  proper  alkalinity.  It  is  pumped  out  of  this 
tank,  or  preferably  from  a  third  tank  into  which  it  overflows  in 
proportion  to  the  amount  treated.  This  last  tank  should  be 
equipped  with  a  heater.  By  careful  regulation  of  the  inflow  of 
juice  and  introduction  of  saturation-gas  one  can  count  on  a  very 
even  and  effective  carbonatation  by  this  method. 

Automatic  control  of  the  inflow  of  the  juice  is  very  advantageous, 
and  often  essential  for  successful  work.  This  is  done  by  having 
the  juice  from  the  second  tank  pass  on  its  way  to  the  scum-pump 
through  a  decantation-tank  provided  with  a  ball-cock.  If  more 
juice  goes  into  the  decantation-tank  than  passes  out,  the  float, 
acting  on  a  lever,  rises  and  shuts  a  throttle-valve  in  the  pipe-line 
discharging  into  the  first  saturation-pan.  This  throttle  shuts  when 


CARBoXATATIOX.  107 

the  float  reaches  its  highest  level,  and  again  opens  when  the  pump 
has  taken  away  sufficient  juice.  The  man  in  charge,  therefore, 
need  not  trouble  himself  with  the  juice-feed,  but  can  devote  his 
whole  attention  to  the  carbonatation  and  can  carry  this  to  the 
proper  point,  being  guided  in  the  regulation  of  the  gas-valve  by 
the  indications  of  tit  rat  ions,  which  should  be  made  frequently. 
It  is  necessary  to  titrate  the  juice  of  the  second  tank  only,  in  the 
first  tank  merely  taking  care  that  the  juice  is  not  completely 
saturated.  Often  only  one  saturation-tank  is  used.  Aside  from 
the  disadvantage  that  working  in  this  way  there  is  more  uncer- 
certainty  of  holding  the  alkalinity  constant,  the  utilization  of 
the  carbon  dioxide  is  very  inefficient.  If  two  tanks  are  used 
the  alkalinity  in  the  first  is  0.15-0.18,  and  in  the  second  0.07- 
0.10.  In  this  case,  the  major  part  of  the  gas  passes  through 
juice  of  an  alkalinity  of  0.1.5-0.18,  which  is  notably  higher  than 
that  of  second  tank.  Using  only  one  tank  with  a  continuous 
carbonatation,  the  alkalinity  must  be  kept  always  at  0.06-0.10. 
Hence,  the  gas  passing  through  juice  of  such  low  alkalinity  will 
be  very  inefficiently  utilized,  as  we  have  shown  previous!}'. 

The  chemical  reactions  occurring  in  continuous  carbonatation 
are  somewhat  different  than  in  the  ordinary  method,  because  the 
first  pan  always  contains  a  fairly  well-saturated  juice.  The 
freshly  defecated  juice  is  always  mixing  in  with  such  liquor,  so 
that  the  definite  stages  of  chemical  change  noted  in  carbonatating 
a  single  tank  do  not  here  appear.  Little  or  no  gelatinous  double 
salts  are  formed,  hence  the  carbonatation  goes  quicker  and  more 
regularly.  Since  quick  carbonatation  is  best  for  the  juice,  this 
continuous  method  of  working  has  advantages  over  the  ordinary 
process.  These  advantages,  however,  are  not  obtained  unless  the 
defecation  is  conducted  with  even  more  care  than  in  the  usual 
process,  since  defecated  juice  entering  the  first  tank  stops  the 
action  of  the  lime. 

Carbonic  acid  is  practically  the  universal  reagent  used  for 
neutralizing  lime.  Experiments  have  been  tried  of  using  car- 
bonic dioxide  first  and  completing  the  saturation  with  sulphurous 
acid,  which  gives  clearer  and  better  juices.  However,  the  out- 


108  BEET-SUGAR   MANUFACTURE. 

come  of  these  investigations  is  that  it  is  seldom  advisable  to 
use  such  procedure,  since  it  increases  the  cost  of  carbonatation 
and  makes  its  supervision  more  difficult. 

Carbonatation  troubles  are  usually  shown  by  the  process  going 
too  slowly.  There  are  many  causes  for  this.  Since  gas  rich  in 
carbon  dioxide  is  the  prime  requisite  for  good  carbonatation,  it 
is  obvious  that  from  gas  of  such  quality  more  carbonic  acid  will 
be  absorbed,  not  only  absolutely,  but  relatively.  It  is  necessary 
on  the  other  hand,  to  introduce  the  required  amount  of  carbonic- 
acid  gas  into  the  juices.  '  If  the  carbonic-acid  pump  is  too  small 
or  is  defective  in  its  action,  the  carbonatation  will  always  be 
insufficient.  The  size  of  the  pump's  cylinder  should  be  large 
enough  so  that  under  normal  conditions  a  relatively  slow  stroke 
is  sufficient,  and  when  there  is  a  leakage  in  casing,  valves,  or  pipes 
it  can  be  compensated  by  quickening  the  stroke.  The  amount  of 
carbonic-acid  gas,  or  the  efficiency  of  the  pump  is  diminished  if  the 
exhaustion  in  the  suction-pipe  is  too  great.  There  is  always  some 
vacuum  in  the  suction-pipe  owing  to  the  resistance  in  the  tube 
itself  and  in  the  washers,  but  this  should  never  be  more  than  is 
equivalent  to  a  water-column  of  about  3  feet.  In  order  to  measure 
it,  and  to  find  readily  any  place  where  there  is  too  much  resist- 
ance, it  is  well  to  insert  water-column  vacuum-gauges  before  and 
behind  each  washer  as  well  as  at  the  pump.  It  is  then  immedi- 
ately apparent  whether  the  greater  resistance  is  caused  by  irregu- 
lar working  of  the  washers  or  by  the  stopping  up  of  the  piping 
by  flue-cinders  from  the  lime-kilns. 

Too  slow  carbonatation,  or  rather  a  lengthening  of  the  duration 
of  the  process,  will  take  place  when  too  much  lime  has  been 
added  to  the  juice;  this  is  likely  to  be  the  case  when  the  milk 
of  lime  has  been  made  too  thick  or  too  much  dry  lime  has  been 
added. 

Besides  these  causes  of  slow  carbonatation  which  can  be  easily 
explained  or  detected,  there  are  others  which  probably  depend  to 
some  extent  upon  the  nature  of  the  diffuser-juice  and  which  are 
much  more  difficult  to  explain.  It  is  very  probable  that  in  this 
case,  again,  the  pectic  substances  exert  some  influence,  because, 


CARBON  ATATION.  109 

when  the  carbonatation-work  is  unsatisfactory  on  account  of  the 
quality  of  the  juice,  it  will  be  found  invariably  that  this  juice  was 
obtained  from  unripe,  over-fertilized,  or  decayed  beets,  and  results 
also  depend  somewhat  on  the  method  of  carrying  out  the  diff user- 
work.  These  pec  tic  substances  when  present  in  large  amount  appear 
to  combine  with  the  lime  and  thicken  the  juice  just  as  the  sugar 
itself  does,  except  that  it  is  more  difficult  to  get  rid  of  this  thicken- 
ing when  caused  by  the  former  substances,  and  for  this  reason  the 
carbonatation  process  is  retarded.  In  such  cases  the  best  pre- 
ventive is  to  change  the  diffuser-work  so  that  the  juices  are  ob- 
tained as  quickly  as  possible  and  at  not  too  high  a  temperature. 
In  every  case  where  the  carbonatation  process  is  lengthened,  no 
matter  what  the  cause  may  be,  the  quality  of  the  juice  is  bound 
to  suffer  both  in  color  and  purity.  For  this  reason  the  cause  of 
the  slow  carbonatation  should  be  removed  as  soon  as  possible. 

Testing  the  escaping  gases  systematically  is  a  great  help  in 
locating  the  cause  of  slow  saturation,  especially  in  continuous 
carbonatation.  By  knowing  the  normal  carbon  dioxide  content 
of  these  gases,  if  poor  absorption  is  the  cause  of  the  trouble  it 
is  at  once  detected.  ' 

Another  undesirable  disturbance  of  the  carbonatation  process 
is  caused  by  a  strong  frothing  of  the  juices.  This  phenomenon 
also  depends  upon  the  quality  of  the  beets  and  the  method  of 
working  the  diffuser  battery,  and  occurs  usually  when  there  is 
a  poor  carbonatation.  It  is  evident,  therefore,  that  both  disturb- 
ances result  from  the  same  cause.  When  the  frothing  is  so 
strong  that  the  space  above  the  juice-level  is  insufficient,  the 
only  remedy  is  to  add  oil  or  other  fatty  substance.  In  continuous 
carbonatation  the  foaming  is  seldom  bad  so  that  little  or  no  oil 
is  needed.  Obviously,  sugar  is  lost  if  foam  is  carried  off  through 
the  vent-pipes  by  the  waste  gases.  Moreover,  appreciable  quan- 
tities of  sugar  will  be  found  in  the  escaping  vapors  even  when 
when  the  juice  does  not  foam.  The  results  of  investigations  into 
these  losses  are  awaited  with  interest. 


CHAPTER  IX. 
TREATMENT  OF  THE  SLUDGE  OR  SCUMS. 

FROM  the  carbonatators  the  juice  is  pumped  to  the  filter-presses. 
Juice-lifters  (monte  jus)  are  no  longer  much  used,  on  account 
of  many  disadvantages,  such  as  uncleanliness,  dilution  of  juice  by 
condensed  steam,  irregular  pressure,  and  consumption  of  power. 
Scum-pumps  are  always  constructed  of  the  plunger  type,  single  or 
double  action,  and  work  either  with  automatic  regulation  or  with 
a  by-pass  worked  by  a  sensitive  safety-valve.  A  good  stone- 
eliminator  must  be  connected  with  the  piping  through  which  the 
juice  is  drawn  to  the  pump,  so  that  not  only  stones  but  also  the 
heavier  sand  will  be  removed  which  would  otherwise  clog  up  the 
pump  and  close  up  the  narrow  canals  of  the  filter-presses.  The 
pressure  at  which  the  pumps  should  operate  depends  upon  the  size 
of  the  filtering-surface  in  the  presses  and  the  nature  of  the  scums. 
It  is  desirable  that  the  pressure  should  not  be  too  great,  say  about 
two  or  three  atmospheres  (30  to  45  lbs.);  as  the  cake  so  formed  is 
most  readily  exhausted  of  its  sugar.  With  poor  scums  and  small 
filtering-surfaces  the  pressure  may  be  raised  to  from  four  to  eight 
atmospheres  (60  to  120  lbs.)«  A  pressure  higher  than  this  is  not 
permissible  on  account  of  danger  of  the  walls  of  the  chambers  of 
the  press  collapsing  if  there  happen  to  be  more  pressure  upon  one 
side  than  the  other.  In  order  to  keep  the  pressure  under  control, 
manometers,  or  gauges,  must  be  placed  on  the  force-pipe  and  on 
the  air-chamber.  In  the  piping  back  of  the  pump  a  gate  valve  is 
placed  to  shut  off  the  juice  in  the  pipes  when  necessary  to  over- 
haul the  pump. 

Filter-presses  are  of  two  types,  chamber  presses  and  frame 
presses.  The  chamber  presses,  in  which  the  juice-canal  is  placed 
in  the  middle  and  the  cloths  are  stretched  by  means  of  cloth- 
screws,  have  the  advantage  that  it  is  possible  to  make  them 

110 


TREATMENT   OF  THE   SLUDGE  OR  SCUMS.  Ill 

tighter  because  at  the  outer  joints  four  layers  of  cloth  come 
together;  whereas  they  possess  the  disadvantage  of  requiring 
considerable  time  for  drawing  over  the  cloth  on  account  of  the 
screwing  arrangement;  moreover,  in  the  slack  spaces  the  cloths 
become  jammed  and  torn.  Frame  presses  are  usually  preferred  in 
which  the  cloths  are  placed  smoothly  over  compartments  between 
frames,  the  filter-press  being  set  up  in  a  few  minutes.  An  objection 
to  this  type  of  press  is  that  there  is  likely  to  be  some  leakage  at 
high  pressures,  although  this  ought  not  to  be  the  case  if  the 
workmen  are  practiced  and  keep  the  frames  clean  and  free  from 
adhering  sludge,  taking  care  that  the  cloths  lie  smoothly  during 
the  closing  together  of  the  chambers;  consequently  it  is  only  in 
the  first  few  weeks  of  a  campaign  that  the  presses  do  not  work 
right.  Another  objection  is  that  the  cloths  wear  badly  at  the 
upper  corners  where  the  chambers  and  frames  are  closest,  and 
this  is  aggravated  because  the  workman  always  tries  to  draw 
the  chambers  together  as  hard  as  possible  in  order  to  close  up  the 
press  well.  It  is  a  matter  of  taste  whether  rubber  or  filter-cloth 
gaskets  are  used  for  the  joints  of  the  juice-ducts.  Both  make 
equally  tight  joints. 

The  size  of  the  filter-presses,  or  the  size  and  number  of  the 
compartments  and  frames,  depends  upon  the  amount  of  work  to 
l)e  done.  The  presses  should  have  capacity  enough  to  permit 
continuous  work.  It  would  be  wrong  to  use  a  large  press  in  a 
small  factory,  or  one  large  press  and  several  smaller  ones,  because, 
in  such  cases,  when  the  large  press  is  just  emptied  there  will  be 
too  much  juice  at  hand  for  the  house  to  take  care  of  advan- 
tageously, while  in  the  other  case  the  juice  dams  up  and  the 
house  is  blocked  when  the  presses  begin  to  fill  up.  Again,  it  is 
equally  foolish  to  use  a  lot  of  little  presses  in  taking  care  of  the 
juice  from  a  large  factory,  because  many  more  workmen  are 
necessary  and  more  cloths  are  worn  out  than  when  there  are 
fewer  and  larger  presses. 

The  size  of  the  chambers  or  frames  varies  between  six  and  ten 
decimeters  (24  to  40  inches)  square.  In  a  single  press,  or  in  one 
division  of  a  double  press,  there  are  between  20  and  40  of  these 


112  BEET-SUGAR  MANUFACTURE. 

divisions,  and  the  thickness  of  the  pressed  cake  is  between  15  and 
30  mm.  (0.6  to  1.2  inches).  In  the  case  of  bad  scums  considerable 
thickness  of  the  cake  is  undesirable,  whereas  with  good  scums  that 
are  easy  to  filter  it  is  well  to  have  a  thick  cake;  as  a  matter  of  fact 
in  some  factories  cakes  thicker  than  30  mm.  are  produced. 

It  is  not  possible  to  state  definitely  just  how  much  filter- 
surface  should  be  calculated  for  the  daily  working  up  of  a  definite 
quantity  of  beets,  because  the  readiness  with  which  the  scums 
can  be  filtered  varies  greatly.  It  is  desirable,  however,  that  as 
large  a  filtering-surface  as  possible  should  be  provided,  so  that  it 
will  be  sufficient,  even  when  there  is  difficulty  with  the  filtration, 
to  keep  the  factory  running  at  its  usual  capacity.  In  this  case 
there  will  be  ample  time  for  a  good  sweetening-off  of  readily 
filtered  scums. 

During  the  campaign  it  is  usually  unnecessary  to  clean  the 
filter-press  ducts  and  strainers.  After  every  campaign,  however, 
they  must  be  examined  and  cleaned,  since  the  holes  of  strainers, 
the  various  ducts,  and  the  discharge-cocks  become  stopped  up  or 
contracted  by  deposits  of  scale.  If  these  passages  cannot  be 
cleaned  by  brushing  and  boring  out,  or  when  such  a  procedure 
proves  too  tedious,  the  strainers  and  frames  can  be  dipped  in  water 
containing  hydrochloric  acid,  or  concentrated  acid  must  be  poured 
through  the  canals.  In  all  cases  they  must  be  well  washed  out 
with  water  so  that  all  traces  of  acid  are  removed,  and  in  order  to 
prevent  the  strainers  from  rusting  they  must  be  varnished  as  soon 
as  dry.  If  there  is  fear  of  the  acid  eating  into  the  strainers  too 
much,  use  may  be  made  of  mechanical  flue-scrapers  for  cleaning 
out  the  holes  which  are  clogged.  In  some  factories  it  is  the  custom 
to  pump  -hot  water  containing  hydrochloric  acid  through  the 
presses  immediately  at  the  close  of  the  campaign;  this  method  of 
cleaning  the  presses  saves  considerable  time,  but  should  be  used  only 
with  great  caution  to  avoid  injuring  pumps,  pipes,  and  different 
parts  of  the  presses. 

The  choice  of  cloth  for  the  filters  is  not  without  influence  upon 
filter-press  work,  but  here  again  opinions  differ.  Whereas  in  one 
factory  a  heavy  cloth  of  as  good  quality  as  possible  is  preferred,  in 


TRKAIMKXT  OF  THE  SLUDGE  OR  SCUMS.      113 

another  a  quite  light  fabric  will  be  used.  As  a  rule  for  the  first 
carbonatation  a  material  made  of  jute  is  used,  because  it  is  cheapest 
and  suffers  little  from  the  influence  of  the  alkaline  juice.  With 
regard  to  the  durability  of  the  cloth,  naturally  the  degree  of 
alkalinity  and  the  temperature  of  the  juice  exert  considerable 
influence.  When  the  scums  are  poor  and  the  cloths  must  be 
frequently  changed  and  cleaned,  preference  should  be  given  to  a 
material  which  is  not  too  light  and  of  not  too  poor  quality  and  which 
washes  well.  When  the  scums  are  as  a  rule  easy  to  filter,  cheaper 
cloths  of  lighter  fabric  are  suitable,  these  being  allowed  to  remain 
in  the  presses  until  worn  out — a  matter  of  perhaps  fourteen  days 
or  longer.  It  goes  without  saying  that  it  is  important  to  have  the 
cloths  of  proper  size,  so  that  they  will  not  crease  or  wrinkle. 

In  many  factories  it  is  customary  to  avoid  changing  single 
cloths  in  a  press,  and  as  a  result  it  is  a  common  error  to  allow  all 
of  the  cloths  to  remain  too  long,  even  until  the  liquid  runs  -through 
turbid.  The  cloths  throughout  the  whole  of  the  press  are  then 
renewed  and  replaced  by  new  ones  which  are  all  of  the  same  kind 
and  possess  equal  filtering  capacity;  either  new  cloths  are  used 
throughout,  or  washed  cloths  are  placed  underneath  and  new 
ones  on  top.  In  this  way  the  press  will  be  filled  uniformly  and 
the  sugar  washed  out  equally  well  from  all  parts. 

Special  washing-machines  are  usually  required  for  washing  the 
eloths.  It  has  proved  very  satisfactory  to  place  them  in  a 
drum  provided  with  compartments;  hot  water  flows  continuously 
through  this  drum  and,  while  the  latter  is  revolving,  the  cloths  in 
the  compartments  partially  filled  with  water  are  thrown  about 
back  and  forth.  Wetting  new  cloths  before  placing  them  on  the 
presses  is  unnecessary  when  jute  is  used. 

In  order  to  give  the  cloths  a  good  surface  to  lie  against,  sheets 
of  perforated  metal  are  screwed  on  the  chambers.  Recently  the 
surface  of  these  chamber-plates  has  been  grooved  without  the 
sieve.  The  advantage  gained  is  that  the  cleaning  of  the  sieve 
and  its  wearing  out  is  obviated  and  the  cloths  are  said  to  last 
as  long. 

The  press-cake  is  formed  in  the  presses  between  the  cloths  by 


114  BEET-SUGAR  MANUFACTURE. 

the  gradual  deposition  of  the  scum  in  uniform  layers  upon  the 
cloths.  The  heavier  particles  of  the  sludge,  such  as  the  coarser 
sand,  sink  to  the  bottom  of  the  section  as  long  as  the  contents 
remain  soft,  and  the  lower  portion  of  the  space  between  the 
cloths  is  filled  rather  more  quickly  than  the  upper  part;  but,  as  a 
general  rule,  where  the  pressure  from  the  pumps  is  not  too  low 
the  cake  is  uniformly  deposited  by  the  current  of  liquor  flowing 
through  the  cloth.  This  is  evident  by  breaking  the  cake  and 
observing  its  differently  colored  layers.  Each  tankful  of  juice 
gives  with  the  separate  carbonatations  a  somewhat  differently 
colored  scum,  so  that  the  press-cake  will  have  a  layer  that  is  more  or 
less  yellow,  followed  perhaps  by  one  which  is  bluish  in  tone.  In  the 
case  of  continuous  carbonatation  the  press-cakes  are  of  uniform  color. 
When  the  entrance-valve  of  an  empty  filter-press  is  opened 
the  juice  runs  in  a  strong  stream  from  the  discharge-cocks.  The 
greater  the  amount  of  sludge  upon  the  cloths,  the  less  penetrable 
they  become,  so  that  as  the  press-cake  increases  in  amount,  the 
slower  the  filtered  juice  runs  off,  and  finally  at  the  end  of  one  or 
two  hours  the  press  becomes  full  and  the  juice  drops  from  the 
cocks  in  very  thin  streams.  The  workman  in  charge  must 
know  from  experience  when  the  press  is  sufficiently  filled.  It  is  a 
waste  of  time  to  allow  a  press  to  work  too  long,  while,  on  the  other 
hand,  a  press  that  is  not  entirely  filled  will  not  permit  a  satisfactory 
exhaustion  of  the  sludge,  and  the  soft  filter-cake  contained  in  the 
press  readily  smears  over  the  cloths  and  frames,  so  that  subse- 
quently the  press  is  likely  to  squirt  and  run  badly.  Since  a  good 
scum-cake,  or  at  least  one  of  relatively  firm  structure,  always 
facilitates  the  work  of  the  exhaustion  of  the  residuum,  it  is  advisa- 
ble always  to  allow  the  press  to  become  as  full  as  possible  even  when 
it  runs  slowly.  It  is  not  possible  to  improve  matters  by  emptying 
the  press  as  soon  as  it  begins  to  run  badly,  for  the  time  spent  in 
removing  the  soft  slimy  mass,  together  with  such  evils  as  subsequent 
leakage,  smearing  the  cloths,  etc.,  more  than  compensates  for  any 
gain  in  the  actual  time  of  filtration;  it  is  advisable  to  calmly  wait 
for  the  press  to  become  reasonably  well  filled,  so  that  it  will  leave  a 
dry  press-cake. 


TREATMENT  OF  THE  SLUDGE  OR  SCUMS.      115 

The  cause  of  slow-running  presses,  or  in  other  words  of  the 
juice  filtering  badly  and  the  undesirable,  soft  consistency  of  the 
press-cake,  is  to  be  sought  either  in  the  nature  of  the  beets  or  the 
method  of  working.  It  has  already  been  mentioned  that  in 
working  up  certain  grades  of  beets  the  diffusion-work  exerts  a 
great  influence  upon  the  consistency  of  the  scum.  When  the 
quality  of  the  beets  is  the  cause  of  the  presses  clogging,  there  is 
some  gain  to  be  sought  in  changing  the  method  of  working  the 
diffusion.  Increasing  the  amount  of  lime  added  to  the  juice  above 
a  certain  limit  has  seldom  met  with  success,  aside  from  the  fact 
that  most  factories  are  unable  to  take  care  of  sludge  much 
in  excess  of  the  ordinary  amount.  Likewise,  slight  sticcess 
is  obtained  by  boiling  up  the  juice,  as  has  been  frequently  recom- 
mended, since  there  is  then  greater  difficulty  in  emptying  presses 
and  the  scum  obtained  is  little,  if  any,  better  than  that  obtained  at 
the«usual  temperature  of  from  SO0  to  90°  C.*  Similarly  changing  the 
alkalinity  of  the  juice  is  of  no  use.  In  short,  it  is  best  to  avoid 
all  useless  experiments  and  merely  try  to  hasten  the  work  by 
changing  cloths  often.  These  difficulties  are  met  with  chiefly  at 
the  beginning  of  the  campaign,  when  it  is  necessary  to  work  up 
beets  which  are  not  quite  ripe  and  with  unpracticed  workman, 
and  the  trouble  as  a  rule  will  shortly  disappear  apparently  of  its 
own  accord. 

A  press-cake,  difficult  to  filter  and  sweeten  off,  often  comes 
from  the  diffusion  juice  of  high  density,  over  15°  Brix,  especially 
that  from  wilted  or  dried  beets.  In  this  case  the  usual  reme  ly  is 
increasing  the  size  of  the  juice  drawings,  which  of  course  causes 
dilution.  Since,  however,  this  increases  the  work  of  the  evaporator 
it  is  better  to  provide  for  this  dilution  by  sending  all  the  sweet- 
water  from  the  filter-presses,  not  needed  for  slaking  the  lime, 
back  to  the  defecators  or  carbonatation  tanks,  whereby  the  car- 
bonatation  will  likewise  be  improved. 

From  the  reactions  during  carbonatation  it  is  clear,  without 
further  explanation,  that  juices  which  have  been  either  insufficiently 

*  175-195°  F. 


116  BEET-STCiAR    MANUFACTURE. 

or  too  completely  saturated  with  carbonic-acid  gas  will  be  difficult 
to  filter.  Consequently  it  is  always  necessary  to  conduct  the 
carbonatation  with  the  greatest  care,  but  especially  when  the 
sludge  itself  is  of  a  nature  which  renders  the  nitration  difficult. 
When  the  presses  run  badly  for  a  temporary  period,  it  may  be 
due  to  juice  from  a  properly  carbonatated  tank  becoming  mixed 
in  pumping  with  juice  from  a  tank  which  has  not  been  properly 
saturated,  owing  to  a  leaky  valve  or  by  the  foaming  over  from  one 
tank  to  another.  Whether  this  is  the  cause  of  badly  filtering 
scums  may  be  determined  by  titrating  the  juice  that  comes  from 
the  press.  Such  juice  will  show  a  considerable  higher  alkalinity 
than  that  coming  from  single  tanks  which  have  been  properly 
carbonatated.  It  is  advisable  to  make  such  control  titrations  at 
frequent  intervals.  A  slight  increase  in  the  alkalinity  of  the  juice 
is  nearly  always  produced  in  the  filter-presses,  because  the  sludge 
encloses  small  amounts  of  caustic  lime  and  lime  sucrate  which 
gradually  dissolve  throughout  the  whole  layer  by  the  juice  that 
is  continually  passing  through  it.  This  alkalinity  amounts,  as  a 
rule,  to  about  0.1  per  cent,  of  lime. 

Soft  cake  is  also  obtained  when  the  pump  does  not  give  high 
enough  pressure,  and  to  guard  against  this  it  is  absolutely  essential 
that  there  should  be  a  manometer,  or  pressure-gauge,  in  the  dis- 
charge-pipe. 

The  amount  of  sugar  left  in  unwashed  filter-cake  varies 
according  to  the  amount  of  sugar  in  the  defecated  juice,  and  to 
the  amount  of  insoluble  lime  sucrate  formed.  Usually  the  scums 
are  composed  of  about  40-50  parts  of  solids  and  50-60  parts  of 
juice.  If  the  latter  contains  10  to  12  per  cent,  of  sugar,  it  is 
evident  that  the  filtered  residue  will  contain  from  6  to  7  per  cent, 
of  sugar. 

The  sweetening-off  of  the  filter-cake  should  work  so  as  to  remove 
the  greater  part  of  the  sugar  and  make  the  sweet  water  from  the 
washing  as  concentrated  as  possible.  This  result  can  only  be  attained 
by  driving  the  juice  out  of  the  cake  through  introducing  water 
into  the  press  itself.  In  some  factories  the  filter-cake  is  removed 
from  the  press,  mashed  with  a  little  water,  and  the  mass  is  then 


TREATMENT    <>F   THE   SLUDGE   OH   SCUMS.  -117 

filtered  again  in  the  press.  By  this  method  of  working,  however, 
a  weaker  sweet  water  is  obtained,  with  the  same  amount  of 
sugar  remaining  in  the  cake  as  when  the  washing  takes  place  in 
the  press  itself.  The  latter  method  has  the  sole  advantage  that 
it  permits  the  use  of  a  simpler  type  of  filter-press. 

Washing  the  cake  may  be  done  in  two  ways:  either  have 
the  water  enter  through  special  canals  placed  on  one  side  of  the 
scum-cake,  penetrate  the  latter  and  flow  away  at  the  other  side, 
or  have  the  water  follow  the  same  course  as  that  taken  by  the 
original  juice,  enter  through  the  centre  of  the  cake,  pass  through 
both  halves  and  flow  away  on  both  sides. 

Indispensable  conditions  upon  which  the  success  of  either 
method  of  washing  depends  are  a  uniform  nature  and  thickness  of 
all  the  scum-cakes  in  one  press  and  evenly  penetrable  cloths.  When 
the  cake  is  thinner  and  softer  at  one  place,  for  example  in  the 
upper  part  of  presses  which  have  been  badly  filled,  more  water 
will  penetrate  these  portions  than  through  the  thicker  and  harder 
parts.  When,  therefore,  the  former  portions  are  already  com- 
pletely sweetened  off,  the  thicker  portions  are  still  likely  to  con- 
tain considerable  sugar.  This  trouble  becomes  more  appreciable 
in  proportion  to  the  amount  of  pressure  employed.  Certainly 
this  unequal  penetration  of  water  into  the  scum-cake  can  never 
be  entirely  prevented,  because,  owing  to  the  construction  of  the 
presses,  even  the  best  and  most  uniform  cakes  will  have  bad  places. 
In  the  case  of  the  chamber  presses  these  bad  spots  are  at  the 
outer  borders  where  the  cakes  are  thinner,  and  at  the  places  where 
the  cloths  are  screwed  together,  where  the  scum-cake  usually 
remains  soft.  In  the  case  of  the  frame  presses  these  spots  are 
found  between  the  iron  frames  and  the  cake,  where  the  adhesion 
of  the  latter  to  the  iron  is  less  than  the  cohesion  of  the  cake 
itself.  Excessive  solidity  of  the  cake  is  also  detrimental,  because 
in  such  cases  the  solution  of  the  sugar  throughout  the  whole 
mass  takes  place  slowly  and  requires  greater  water-pressure. 
Consequently  every  variation  in  the  thickness  of  the  scum-cake 
then  makes  itself  objectionable  to  an  increased  extent. 

In  order  to  avoid  troubles  from  variable  or  excessive  pressure, 


118  BEET-SUGAR  MANUFACTURE. 

the  scum-pumps  in  some  factories  are  not  allowed  to  work  directly 
upon  the  filter-presses.  The  juice  is  pumped  into  a  tank  placed 
high  and  provided  with  a  return-flow  pipe.  From  this  tank  the 
juice  runs  into  the  presses  with  the  relatively  low  but  always 
uniform  pressure  of  from  one  to  one  and  one-half  atmospheres.* 
It  is  said  that  under  these  conditions  the  presses  work  better  and 
that  it  is  then  much  easier  to  remove  the  sugar  from  the  filtered 
residues. 

High  water-pressure  is  above  all  things  incompatible  with  a 
satisfactory  removal  of  sugar  from  the  cake;  but  where  low  pressures 
are  used  it  takes  very  much  longer  to  remove  the  sugar  and  a 
larger  number  of  presses  is  necessary. 

Many  believe  it  is  better  to  operate  the  pump  for  sweeten- 
ing-off  at  a  pressure  slightly  higher  than  that  of  the  scum- 
pump,  and  possibly  in  many  cases  this  rule  may  work  satis- 
factorily, but  it  is  more  correct  to  adjust  the  pressure  of 
the  sweetening-off  pump  so  that  in  a  given  time  a  definite 
volume  of  the  sweet-water  will  be  obtained.  Consequently 
the  pressure  of  the  latter  should  be  regulated  according  to 
the  nature  of  the  scum-cake  and  its  thickness,  but  taking 
care  that  this  pressure  shall  not  be  made  too  high  so  that  any 
inequalities  in  the  cakes  will  make  trouble.  It  may  be  assumed 
that  the  highest  pressure  for  efficient  washing  with  the  least  water 
should  not  exceed  about  two  atmospheres.  Every  increase  of 
pressure  above  this  point  causes  increased  volume  and  dilution 
of  the  sweet-water  and  leaves  the  same  amount  of  sugar  in  the 
press-cake. 

The  time  required  for  sweetening-off  the  cake  to  1  per 
cent,  is  quite  long.  With  low  pressures  it  can  be  assumed  to 
be  about  20  to  30  minutes  with  good  slimes,  and  about  100  to 
150  parts  of  sweet-water  will  be  obtained  from  100  parts  of  scum. 
If  the  pressure  be  increased,  as  must  always  be  the  case  with  poor 
scums,  then  the  volume  of  the  sweet-water  is  increased  to  a  con- 
siderable extent  and  the  liquid  flows  much  more  slowly  through  the 

*  15-22  Ibs.  per  square  inch. 


TREATMENT  OF  THE  SLUDGE  OR  SCUMS.       119 

press;  it  is  then  usually  not  practicable  to  reduce  the  sugar-content 
to  an  average  of  but  one  per  cent.  In  German  factories  the 
extraction  is  considered  satisfactory  when  the  sugar-content  is 
reduced  to  from  l£-2  per  cent. 

The  question  as  to  whether  it  is  advisable  to  use  hot  or  cold 
water  for  washing  the  cake  has  not  yet  been  definitely  settled. 
It  is,  however,  hardly  probable  that  the  temperature  of  the  water 
exerts  any  influence  upon  the  purity  of  the  sweet-water  obtained 
from  the  presses,  provided  pure  water  is  used.  As  there  are  large 
amounts  of  pure  hot  water  available  in  the  beet-sugar  factory  from 
condensed  steam,  it  is  usually  best  to  use  it  without  going  to  the 
trouble  of  cooling.  The  only  advantage  to  be  obtained  from  using 
cold  water  is  perhaps  that  the  filtered  scums  will  cool  down 
so  that  the  workmen  will  be  less  inconvenienced  by  steam  while 
discharging  the  presses.  Cold,  hard  well-water  should  be  avoided 
as  far  as  possible,  for  when  such  water  entering  the  hot  compart- 
ments comes  in  contact  with  the  lime  contained  in  the  juices,  pre- 
cipitates will  be  formed  that  will  tend  to  clog  up  the  ducts  and 
strainer  of  the  press,  besides  making  the  cloths  stiff.  It  is  true 
that  these  lime  deposits  may  be  formed  when  using  condensed 
water  in  case  the  latter  contains  ammomium  carbonate  instead  of 
ammonia.  Ammonium  carbonate  is  formed  in  large  amounts 
when  the  juice  is  over-carbonated  in  the  second  carbonatation. 

It  is  evident  that  so  much  water  used  in  washing  will  to  some 
extent  redissolve  the  non-sugars  that  have  been  precipitated  from 
the  defecated  juice,  and  consequently  the  last  of  the  sweet-water 
obtained  from  the  presses,  in  which  the  small  amount  of  juice 
remaining  in  the  sludge  has  been  diluted  with  a  large  amount  of 
water,  will  be  of  a  lower  purity  than  the  first.  The  purity,  however, 
remains  sufficient  to  yield  a  massecu'te  which  will  readily  crystallize. 
There  is,  therefore,  absolutely  no  objection  to  washing  the  residues 
thoroughly,  provided  the  number  of  presses  is  sufficiently  large  and 
it  does  not  make  too  much  dilution. 

Which  method  of  washing  the  residues  is  to  be  chosen,  i.e., 
whether  the  water  should  be  allowed  to  pass  through  special  ducts 
in  the  press  and  then  percolate  through  the  whole  cake,  or  whether 


120  BEET-SUGAR  MANUFACTURE. 

the  water  should  follow  the  juice-ducts  and  pass  through  half  of 
the  cake,  depends  upon  particular  conditions.  In  general  the 
former  method  is  preferable  with  well-arranged  presses,  because 
under  otherwise  similar  conditions  the  cake  is  more  uniformly 
sweetened  off  and  the  juice  is  less  diluted.  Special  precautions 
should  be  taken  to  see  that  the  juice-valve  is  tightly  closed 
during  sweetening-off  and  that  during  filtering  the  water-valve 
is  well  shut.  If  the  former  has  been  left  open  sweetening-off  is 
impossible;  if  the  water-valve  leaks  the  juice  is  badly  diluted. 
Unremitting  vigilance  over  these  valves  is  essential. 

In  those  factories  where  milk  of  lime  is  used  for  defecation 
the  weaker  portions  of  the  sweet-water  should  be  collected  sep- 
arately and  used  for  slaking  lime.  Since  for  slaking  one  part  of  lime 
from  5-6  parts  of  water  are  required,  and  one  part  of  lime  yields 
about  3J  to  4  parts  of  sludge,  it  is  evident  that  in  such  cases 
there  need  be  no  particular  apprehension  with  regard  to  excessive 
dilution  of  the  sweet-water,  for  an  amount  for  water  equal  to  150 
per  cent,  of  the  weight  of  sludge  is  necessary  for  the  slaking  of 
the  lime.  On  the  other  hand,  in  factories  employing  dry  defecation 
every  unnecessary  dilution  of  the  sweet-water  is  to  be  avoided,  for 
in  such  cases  there  is  no  especial  use  for  the  more  dilute  portions 
of  it.  All  of  the  water  must  then  be  worked  up  with  the 
juice,  and  if  it  is  diluted  too  much,  the  advantage  gained 
from  dry  defecation,  especially  with  regard  to  saving  of  fuel, 
is  lost. 

However,  a  thorough  sweetening-off  of  the  scums  from  the 
dry-defecation  process  without  thinning  the  juice  excessively 
has  been  proposed  in  which  the  sweet-waters  are  separated  accord- 
ing to  their  density.  The  first  sweet-water  which  is  rich  in  sugar 
goes  as  usual  to  the  juice,  but  the  later  water  is  cut  out  and 
utilized  for  sweetening-off  the  next  press,  and  so  on.  Appro- 
priate devices  make  this  system  automatic. 

The  cake  that  is  emptied  from  the  presses  falls  either  into  cars 
(by  means  of  which  it  is  carried  out  and  deposited  in  heaps),  into 
a  screw  conveyor,  or  into  a  scum-mixer  in  which  it  is  mashed  into 
a  thick  paste.  The  paste  can  then  be  flushed  out  with  waste  water 


TREATMENT  OF  THE  SLUDGE  OR  SCUMS.  1^1 

of  the  factory,  or  be  carried  to  any  desirable  place  by  means 
of  pumps.  Cakes  obtained  by  the  use  of  a  minimum  amount  of 
lime  make  the  most  desirable  fertilizers,  because  the  amounts  of 
phosphorus  and  nitrogen  contained  in  them  are  relatively  higher 
than  in  cakes  with  an  excessive  amount  of  lime. 


CHAPTER  X. 
FINAL  CARBONATATION  AND  FILTRATION. 

THE  juice  from  the  scum-presses  is  sent  to  the  tanks  for  a  second 
carbonatation.  Since  this  juice  has  become  cooled  in  passing 
through  the  filter-presses  and  canals,  it  must  be  reheated,  exhaust- 
steam  reheaters  being  obviously  best  suited  for  the  purpose.  This 
reheating  should  be  carried  to  boiling  temperature,  since  it  is 
important  that  thin  juice  should  be  kept  at  about  100°  (212°  F.) 
after  the  first  filtration.  This  high  temperature  is  not  only  desirable 
for  the  action  of  lime  on  the  non-sugars,  but  it  is  necessary  to 
prevent  the  calcium  carbonate  formed  in  the  second  and  third 
carbonatations  from  going  into  solution  as  acid  carbonate. 

If  lime  is  added  in  the  second  carbonatation  the  heating  must 
take  place  first,  to  avoid  heating  with  excess  of  1  me,  dnce 
some  lime  sucrate  is  precipitated  out  of  juice  saturated  with 
lime  at  70°-80°  (158°-176°  F.)  when  such  juice  is  heated 
to  100°.  Usually  about  0.25%  of  milk  of  lime  is  added  to  the 
juice  before  the  second  carbonatation,  but  such  addition  of  lime 
is  generally  of  no  perceptible  use,  since  the  lime  still  in  solu- 
tion at  this  high  temperature  serves  to  carry  on  the  decompo- 
sition of  the  non-sugars.  When  dry  defecation  is  used  for  the 
first  carbonatation,  this  second  addition  of  lime  is  entirely  omitted 
to  avoid  preparing  milk  of  lime  especially  for  this  purpose;  putting 
dry  lime  directly  into  the  hot  juice  would  make  conditions  favorable 
for  forming  much  insoluble  sucrate  and  consequently  is  not 
advisable. 

The  second  carbonatation  can  be  carried  out  most  conveniently 
as  a  continuous  process  and  by  using  three  tanks,  or  two,  arranged  so 

122 


FINAL  CARBOXATATION  AND  FILTRATION*.  123 

that  the  juice  overflows  from  one  to  the  other,  one  heater  being  used. 
The  juice  is  heated  to  the  proper  temperature  in  the  heater  and 
flows  into  the  first  tank,  where  it  is  saturated  with  gas,  usually 
after  lime  has  been  added;  after  flowing  over  into  the  second  tank  it 
Ls  pumped  off.  A  third  carbonatation  is  carried  out  like  the  second, 
the  most  important  condition  being  that  the  same  high  temperature 
is  maintained. 

Where  only  one  after-carbonatation  is  made,  it  is  either  done 
with  carbonic  acid  alone  or  together  with  sulphurous  acid.  When 
two  after-carbonatations  are  made,  in  the  first  only  carbonic  acid 
is  used,  in  the  second  carbonic  acid  alone,  sulphurous  acid  alone, 
or  both  together. 

There  has  been  much  dispute  whether  one  or  two  after-carbo- 
natations should  be  used.  It  is  not  to  be  denied  that  the 
alkalinity  can  be  more  carefully  regulated  and  any  injurious  in- 
fluence of  excessive  carbonatation  on  the  precipitates  be  more 
easily  avoided  by  two  carbonatations  rather  than  one. 

Two  saturation-plants,  however,  make  the  work  slower  and 
require  more  supervision.  Many  factories  do  well  with  one  final 
carbonatation. 

A  second  after-carbonatation  must  always  be  made  if  the  juice 
to  be  treated  contains  magnesia.  Magnesia  always  goes  into 
solution  if  the  juice  is  gased  so  that  the  alkalinity  falls  below  0.05, 
apparently  forming  an  ammonium-magnesium  carbonate,  or  a 
double  carbonate  which  decomposes  during  the  evaporation  of  the 
juice,  forming  insoluble  magnesium  carbonate.  In  such  cases  the 
alkalinity  of  the  second  carbonatation-juice  (in  the  first  after- 
carbonatation)  must  be  kept  above  0.05  per  cent.,  the  proper 
alkalinity  not  being  made  till  the  juice  is  filtered. 

There  is  a  great  deal  of  dispute  also  as  to  how  alkaline  the  thin 
juice  should  be  made.  Some  recommend  a  high  alkalinity,  others 
a  carbonatation  almost  to  neutrality.  To  answer  the  question 
properly,  the  behavior  of  alkaline  and  neutral  juice  during  evapora- 
tion should  be  studied,  as  well  as  that  of  the  non-sugars  precipitable 
during  carbonatation  in  juice  of  different  concentrations. 

If  thin  juice  is  saturated  with  sulphurous  acid  to  the  neutral 


124  BEET-SUGAR  MANUFACTURE. 

point,  no  doubt  it  has  a  brighter  color  than  alkaline  juice,  but  the 
color  of  the  juice,  especially  that  of  thin  juice,  which  in  the  course 
of  the  process  of  sugar-making  can,  and  actually  does,  alter  very 
much,  cannot  be  taken  as  a  standard  for  guidance  in  treating  such 
juice. 

During  evaporation  juice  in  practically  all  sugar-houses  is 
exposed  for  some  time  to  temperatures  over  100°  (212°  F.),  the 
temperature  of  the  juice-heaters  in  many  houses  rising  as  high  as 
115°  (239°  F.)  or  even  to  120°  (248°  F.),  and  likewise  it  is  at  more 
than  100°  in  the  first  vessel  of  the  multiple-effect  apparatus.  It> 
is  very  doubtful  whether  neutral  or  weakly  alkaline  juices  Should 
be  exposed  to  such  high  temperatures,  for  the  alkalinity  is  con- 
tinually becoming  less  during  evaporation.  Consequently  neutral 
juices  almost  invariably  become  faintly  acid  and  a  noticeable 
inversion  takes  place,  which  is  evident  by  the  darkening  of  the 
juice.  Juices  of  proper  alkalinity,  on  the  contrary,  suffer  no  per- 
ceptible decomposition  during  evaporation  if  the  temperature  does 
not  exceed  the  familiar  limit  of  115°-120°  (239°-248°  F.),  but  they 
are  even  improved  by  this  high  temperature,  as  the  alkalies  act 
energetically  on  the  non-sugars  which  are  not  thoroughly  decom- 
posed in  defecation,  such  as  amides  and  albumens.  Such  alkaline 
juices  as  a  rule  also  show  a  noticeable  falling  off  of  the  alkalinity, 
but  it  does  not  reach  neutrality,  and  it  is  not  caused  by  decom- 
position of  sugar,  but  by  combinations  of  acids  formed  from  the 
non-sugars  with  the  alkalies,  or  on  account  of  the  escape  of  ammonia 
either  previously  present  or  just  produced  by  these  reactions. 
Hence  that  process  is  completed  during  evaporation  which  would 
have  taken  place  in  the  strongly  alkaline  and  defecated  juice  if  the 
necessary  time  and  space  had  been  available. 

Without  anticipating  the  question  of  making  the  sirup  from 
the  evaporators  strongly  or  weakly  carbonated,  it  should  be  settled 
now  as  to  whether  it  is  .better  to  remove  the  last  portions  of  lime 
carbonates  and  sulphites  from  the  thin  liquor  or  from  the  sirup. 
The  deciding  point  is  the  relative  solubilities  of  these  substances  in 
sugar  solutions,  for  a  thorough  carbonatation  of  the  thin  liquor 
can  be  advantageous  only  provided  these  lime  salts  are  less  soluble 


FINAL    CARBOXATATIOX    AM)    FILTRATION.  125 

in  thin  juice  than  in  sirup.  It  happens  that  almost  all  of  the 
difficulty  soluble  lime  salts  are  less  soluble  in  concentrated  sugar 
solutions  than  in  the  more  dilute,  and  daring  evaporation  of  the 
thin  juice  the  carbonates,  sulphites,  and  other  lime  salts  are 
continually  depositing  on  the  heating-tubes  of  the  evaporating- 
apparatus,  irrespective  of  whether  the  thin  juice  is  neutral  or 
alkaline. 

All  considerations,  therefore,  are  in  favor  of  an  alkaline  juice, 
and  one  so  alkaline  that  the  uncarbonatated  intermediate  sirup,  or 
"mittelsaft,"  is  still  alkaline.  Hence  it  is  not  good  practice  to  pre- 
scribe a  certain  fixed  alkalinity  for  the  thin  liquor;  this  alkalinity 
should  vary  much  according  to  the  characteristics  of  the  juice  and 
its  behavior  in  evaporation,  but  it  is  possible  to  set  upper  and 
lower  limits  to  this  variation.  The  upper  limit  will  be  that  alka- 
linity due  to  the  free  lime  and  sucrate  present;  the  lower  limit 
must  be  set  with  reference  to  the  alkalinity  of  the  uncarbonated 
intermediate  sirup,  or  "mittelsaft/'  If  a  certain  fixed  value  has 
been  found  suitable  (say  0.05-0.10  or  thereabouts),  the  alkalinity 
of  the  thin  liquor  must  be  raised  or  lowered  accordingly  as  the 
alkalinity  of  the  sirup  begins  to  sink  under  normal  or  as  it  becomes 
too  alkaline.  Ordinarily  when  the  alkalinity  of  the  juice  is  0.03 
to  0.05  per  cent.,  as  indicated  by  phenolphthalein,  very  little  or 
no  lime  is  present  in  the  caustic  state  (usually  being  in  combination 
as  salts).  The  most  of  the  alkalinity,  therefore,  is  caused  by  fixed 
alkalies,  organic  bases,  and  ammonia.  If  the  composition  of  the 
juice  makes  necessary  an  energetic  after-treatment  of  alkalies  or 
free  lime  in  the  evaporators,  as  when  working  up  unripe  or  rotten 
beets,  the  highest  suitable  limit  should  be  set  for  the  alkalinity  of 
juice  and  sirup.  Obviously  in  such  cases  the  fact  should  also  be 
taken  into  consideration  that  strongly  alkaline  juice  will  form  a 
heavy  scale  in  the  evaporators;  hence,  if  the  evaporation  is  much 
retarded  by  this,  the  alkalinity  should  be  lowered. 

As  far  as  the  purity  and  good  working  qualities  of  the  juice 
are  concerned,  it  makes  no  difference,  in  working  at  the  final  high 
alkalinity  as  recommended,  whether  the  final  carbonatatioti  ie 
completed  with  carbonic  or  sulphurous  acid.  Carbonic  acid  has 


126  BEET-SUGAR  MANUFACTURE. 

the  advantage  of  simplicity  and  cheapness,  saving  the  sulphurous 
acid  for  the  finished  sirup  or  the  "mittelsaft." 

If  two  final  carbonatations  are  considered  expedient,  the  al- 
kalinity of  the  first  should  be  about  0.01-0.02  per  cent,  higher  than 
that  of  the  thin  juice,  so  that  in  the  second  carbonatation  there 
will  remain  some  work  for  the  gas. 

Whether  two  carbonatations  or  only  one  is  made,  a  double 
filtration  of  the  thin  juice  must  always  follow  to  insure  absolutely 
clear  juice  for  evaporation.  Filter-presses  are  usually  employed  for 
the  first  filtration,  with  cloths  of  closely  woven  cotton  flannel,  jute, 
or  linen.  For  this  filtration  it  is  better  to  use  filter-presses  without 
sweetening-off  passages,  because  such  passages  have  the  disad- 
vantage that  if  the  juice  runs  turbid  from  a  discharge-cock,  there 
is  no  means  of  shutting  off  the  chamber  which  is  filtering 
badly.  If  the  cock  is  closed,  the  cloudy  juice  will  run  through 
the  sweetening-off  passage  into  other  chambers  and  make  them 
run  turbid. 

This  simple  type  of  press  naturally  can  only  be  sweetened  off 
through  the  scum-openings,  but  usually  it  is  decidedly  inadvisable 
to  sweeten  off  second  carbonatation-scums.  If  no  lime  is  added, 
the  amount  of  cake  is  very  small,  scarcely  0.1%  of  the  beets,  so 
that  the  sugar  loss,  even  if  the  sugar  in  the  cake  is  considerable,  is 
hardly  worth  taking  into  account.  If,  owing  to  addition  of  lime, 
there  is  a  larger  amount  of  cake,  it  is  better  to  send  it  to  the  first 
carbonatation-tanks  than  try  to  sweeten  off  in  the  second  filter- 
presses.  It  suffices  to  give  these  latter  a  simple  steaming. 

The  sugar-content  of  the  filter-cake,  unsweetened  but  steamed 
out,  is  usually  high,  between  4  and  7  per  cent.,  because  almost 
always  it  contains  insoluble  calcium  sucrate.  The  filtration  after  the 
second  carbonatation  usually  presents  no  difficulties,  so  that  a 
small  filtering-surface  is  sufficient.  Once  in  a  while  the  presses 
suddenly  begin  to  run  badly  or  filter  slowly,  complete  cakes  are 
not  formed,  and  a  small  amount  of  stickier  scum  appears  on  the 
cloths.  This  trouble  comes  ordinarily  when  the  first  carbonatation 
has  a  badly  filtering  scum,  and  is  an  especial  characteristic  of  too 
much  gas  in  the  first  carbonatation.  Magnesium  carbonate  then 
goes  into  solution,  as  already  stated,  this  again  separating  in  the 


FINAL  CARBOXATATIOX  AND  FILTRATION.  127 

second  carbonatation.  The  magnesium  carbonate  so  precipitated, 
as  well  as  the  other  magnesium  salts  which  separate  out  of  solution, 
are  always  of  a  slimy  nature  and  make  filtration  more  difficult  the 
greater  their  proportion  to  the  calcium  carbonate  present. 

Filter-presses  are  less  suited  for  the  second  filtration  of  thin 
j  uices.  Usually  the  improved  form  of  bag  filters  or  a  filter  apparatus 
having  the  maximum  filtering-surface  in  the  least  space  and  per- 
mitting filtration  under  minimum  pressure  is  employed.  Low 
pressure  is  vital  for  retaining  the  more  minute  scum-particles  in 
the  cloth.  What  advantage  one  make  of  apparatus  has  over 
another  depends  on  its  convenience  for  changing  cloths  and  the 
retentiveness  of  the  cloths  or  bags. 

A  very  good  and  reliable  filtration  can  be  made  with  gravel, 
coarse  sand,  or  similar  fine-grained  substance,  in  filters  like 
those  in  which  bone-black  is  used,  or  in  sand  filters  of  special  con- 
struction. These  latter  filters  should  be  so  built  as  to  require  no 
hand  labor  for  washing  the  sand  either  in  the  filter  or  in  special 
apparatus.  Filtering  through  fragments  of  cork,  the  juice  enter- 
ing at  the  bottom  and  forcing  its  way  upward  through  the  cork, 
which  floats  in  the  upper  part  of  the  filter,  is  scarcely  used  now, 
nor  is  filtering  through  wood  chips  and  excelsior. 

All  these  filters  work  well  if  handled  intelligently,  providing 
the  juice  holds  little  scum.  They  are  unsuitable  for  treating 
any  large  amount.  The  customary  methods,  using  filter-presses, 
are  worth  most  consideration. 

Often  something  is  added  to  the  thin  juice  (and  later  to  the 
thick  juice)  to  increase  the  efficiency  of  the  filters  by  coagulating 
the  finer  scum-particles,  particularly  those  which  quickly  slime 
up  the  cloths.  Sawdust,  cellulose,  and  infusorial  earth  are  suit- 
able for  this  purpose.  Care  must  be  taken  that  these  materials 
are  pure  and  do  not  neutralize  weakly  alkaline  juices.  In  cer- 
tain cases  they  must  be  first  digested  with  soda  lye  to  purify  them; 
as  a  rule  this  addition  of  material  is  considered  unnecessary. 

Two  canals  should  be  provided  for  every  thin-liquor  filter,  one 
for  carrying  the  perfectly  clear  juice  flowing  to  the  evaporators, 
the  other  for  taking  the  cloudy  juice,  which  runs  off  particularly 
at  the  start  of  the  filters,  back  to  the  second  carbonatation-tanks. 


CHAPTER  XI. 
OTHER  PURIFYING  AND  CLARIFYING  AGENTS. 

BESIDES  lime  and  carbonic  acid  or  sulphurous  acid,  many  other 
agents  have  been  recommended  for  purifying,  decolorizing,  and 
clarifying  the  juice.  A  list  of  the  different  substances  tried  would 
amount  to  approximately  300;  of  which  number  40  are  made 
up  of  the  different  sulphur  acids  and  their  salts,  25  are  the  phos- 
phorus acids  and  their  compounds,  23  are  the  different  organic 
acids  and  their  salts,  47  are  alkalies,  alkaline  earths  and  their 
compounds,  69  are  metals  and  metallic  ^alts,  56  are  organic  sub- 
stances, and  15  are  substances  prepared  electrolytically. 

These  agents  have  been  used  partly  in  the  diffusion  battery, 
partly  upon  the  crude  juice  in  the  defecation,  and  upon  both  thin 
juice  and  sirup.  In  practice  none  of  these  different  chemicals  have 
continued  in  use.  Disregarding  the  majority  of  the  recommenda- 
tions, which  are  senseless,  it  can  be  said  that  whereas  in  certain 
directions  many  of  these  chemicals  are  actually  efficient,  their  use 
would  be  limited  to  certain  definite  conditions,  and  in  the  majority 
of  cases  they  are  altogether  too  expensive  in  proportion  to  their 
efficiency.  In  certain  cases  poisonous  substances  would  be  intro- 
duced into  the  juice  which,  even  if  not  detected  in  the  sugar,  would 
be  present  in  the  molasses,  making  it  worthless  as  cattle-fodder. 

Since  there  is  no  object  in  purifying  diffusion-juice  previous  to 
defecation,  any  purifying  agent  should  show  its  action  chiefly  where 
the  non-sugars,  upon  which  it  would  be  supposed  to  act,  are  present 
in  the  largest  amount,  namely,  in  the  molasses.  As  a  matter  of 
fact  most  of  the  agents  recommended  have  shown  themselves  to 
be  either  without  any  purifying  action,  or  else  the  action  is  so 
slight  that  the  chemicals  are  too  expensive  to  use. 

Only  relatively  few  substances  could  be  used  to  advantage  with 

128 


OTHER  PURIFYING   AND   CLARIFYING   AGENTS.  12!) 

certain  thin  or  thick  juices.  Of  such  substances  the  most  efficient 
are  the  carbonates  and  acid  sulphites  of  the  alkalies,  or  caustic 
alkalies  which  transform  the  excessive  amounts  of  organic  lime 
salts  into  the  corresponding  alkali  salts,  and  phosphoric  acid 
which  precipitates  lime  as  calcium  phosphate.  Baryta  is  used  to 
effect  the  precipitation  of  sulphurous  and  certain  organic  acids; 
both  it  and  barium  chloride  are  said  to  exert  a  favorable  influence 
upon  the  crystallization  of  the  sugar.  Magnesia,  to  which  favorable 
action  was  attributed  at  one  time,  is  inferior  to  lime  both  with 
respect  to  the  juice-purification  and  the  filtration  of  the  scums, 
without  having  other  advantage.  Alumina  acts  as  a  clarifying 
agent  and  produces  a  clear  juice;  tannin  precipitates  albumins  to 
the  extent  that  they  are  present  in  the  juice;  and  cinders,  lignite 
and  charcoal  clarify  the  juice  without  purifying  it.  As  decolor- 
izing agents,  besides  sulphurous  acid,  there  should  be  mentioned 
hydrosulphurous  acid  and  ozone  with  or  without  simultaneous 
application  of  bone-char  powder.  Recently,  commercial  hy- 
drosulphites  have  been  introduced,  especially  sodium  and  calcium 
hydrosulphites.  They  bleach  juices  eyen  if  they  are  alkaline, 
their  action  on  the  natural  coloring  mat t(M'rf  being  very  marked, 
although  they  do  not  affect  the  characteristic  caramel  color  re- 
sulting from  the  decomposition  of  sucrose  and  invert  sugar. 
The  hydrosulphites  are  especially  efficient  if  introduced  in  the 
vacuum  pan,  because  here  the  objectionable  return  of  the  dark 
color  from  oxidation  of  the  air  is  prevented.  0.01  part  of  Hy- 
drosulphite  for  100  parts  of  sugar.  Furthermore, 'the  salts  of  the 
heavy  metals,  particularly  those  of  zinc,  tin,  and  lead,  effect  some 
decolorization. 

The  use  of  double  silicates  of  limo  and  alumina,  either  the 
minerals  or  artificial  compounds,  for  removing  potassium  and 
-sodium  from  the  juice  is  theoretically  interesting  but  not  yet 
tried  out  in  practice.  By  filtering  thin  or  thick  juices,  sirup  or 
molasses  over  such  coarsely  powdered  silicates,  these  liquors  give 
up  their  alkalies  forming  the  corresponding  lime  salts.  There 
is  actually  no  purification  of  the  juice1,  but  only  a  transformation 
of  its  alkaline  salts  into  lime  salts,  which  do  not  hinder  the  crys- 


130  BEET  SUGAR  MANUFACTURE. 

tallization  of  the  sugar  so  much,  and  are  not  so  melassagenic  as 
the  alkaline  salts.  On  the  other  hand,  the  lime  salts  alter  the 
characteristics  of  juices  and  sirups,  making  them  more  viscous 
and  harder  to  work  in  the  vacuum  pan.  Hence,  it  is  very  ques- 
tionable whether  this  process  can  be  considered  an  important 
improvement.  There  seems  no  profit  in  using  these  silicates, 
although  they  can  be  renewed  easily  by  treatment  with  a  calcium 
chloride  solution,  nor  is  much  gained  by  recovering  the  potassium 
chloride. 

Electrolysis,  particularly  in  the  case  of  the  crude  juice,  with 
lead  or  zinc  electrodes  and  simultaneous  use  of  dialysis,  exerts  a 
favorable  action;  but  such  a  process  is  far  too  expensive  and  the 
sugar-losses  are  altogether  too  great,  so  that  this  electrodialysis 
cannot  find  permanent,  practical  application. 

Formerly  acids,  such  as  oxalic,  phosphoric,  or  even  hydrochloric 
acid,  were  sometimes  introduced  into  the  diffusers  in  order  to 
reduce  the  solubility  of  those  substances  which  cause  the  difficult 
filtration  of  the  scums  from  the  carbonatated  juice.  The  success 
obtained  from  use  of  these  chemicals  is  doubtful;  probably  their 
chief  effect  lies  in  the  injury  to  the  walls  of  the  diffusers.  The  use 
of  such  antiseptic  agents  as  phenol  or  formaldehyde  to  prevent 
evolution  of  gas  in  the  diffusers,  or  in  fact  any  fermentation  of  the 
juice,  is  altogether  ineffectual,  for  it  is  possible  to  add  such  sub- 
stances only  in  very  small  amounts,  or  else  they  become  too 
expensive,  and  moreover,  they  impart  to  the  sugar  an  unpleasant 
taste  and  odor. 


CHAPTER  XII. 
EVAPORATION. 

BY  means  of  evaporating  apparatus  the  thin  juice  is  con- 
centrated from  a  density  of  12-13°  Brix  (6.8-7.40  Be*)  to  a  sirup  of 
about  60°  Brix  (33°  Be.),  about  80%  of  water  being  removed, 
reckoned  on  the  weight  of  the  juice.  Factories  having  evaporators 
whose  heating-surface  is  small  or  inefficient  do  well  to  get  a  con- 
centration to  50°  (27.7°  Be.),  but  obviously  they  waste  steam  and 
coal.  A  proper  evaporating-plant  should  be  designed  to  give 
under  unfavorable  circumstances  a  sirup  of  at  least  55-60  Brix. 
Concentrations  as  high  as  65-70°  (35.6^38.1°  Be.)  are  not  advisable, 
because  such  heavy  sirup  makes  the  vacuum-pan  work  harder, 
and  it  also  may  happen  that  by  cooling  in  the  pipes  crystals  are 
deposited  and  stoppages  may  occur. 

The  average  quantity  of  thin  liquor  which  is  obtained  ordinarily, 
reckoned  for  a  factory  using  dry  defecation  and  two  per  cent,  of 
lime  per  100  kilos  (220  Ibs.)  of  beets,  is  about  as  follows: 

Obtained  from  the  diffusion:  about  105  liters 

(27.7  gals.) 110  kg.  (242  Ibs.) 

Sweet  water  from  filter-presses,  125%  of  8% 

scums 10  kg.  (22  Ibs.) 

Various  concentrates 2  kg.  (4.4  Ibs.) 


Total  thin  juice 122  kg.  (268.4  Ibs.) 

In  factories  using  defecation  with  milk  of  lime,  the  lime  used  up 
is  somewhat  more  and  the  amount  of  sweet  water  somewhat  greater. 
Moreover,  there  is  usually  not  enough  of  the  latter  to  slake  the 

131 


132  BEET-SUGAR  MANUFACTURE. 

lime,  so  that  the  yield  under  these  conditions  must  be  reckoned 
at  least  125  kg.  of  juice  per  100  kg.  of  beets. 

Diffusion-juice  which  has  a  sugar-content  of  from  12  to  13 
per  cent,  consequently  gives  a  thin  liquor  of  from  10.5  to  11.5 
per  cent,  of  sucrose.  In  the  average  factory  working  up  550  tons 
of  beets  a  day  there  are  about  C87.5  tons  of  thin  liquor;  in  the 
larger  ones  working  up  1,100  to  2,200  tons  per  diem  there  will 
be  from  1,375  to  2,750  avoirdupois  tors  of  thin  liquor  to  con- 
centrate. 

For  evaporating  such  enormous  amounts  of  water  there  is  in 
existence  apparatus  of  many  different  makes  and  principles  of 
working.  The  heating-surface  of  the  ordinary  types  consists  of 
tubes  held  in  position  by  tube-plates.  In  vertical  apparatus  the 
juice  is  evaporated  in  the  tubes;  in  the  horizontal  types  it  passes 
over  the  outside  of  the  tubes.  In  the  former  the  length  of  the 
tubes  is  usually  1.25-1.50  meters  (4-5  ft.),  in  the  horizontal  evapo- 
rators 3-4  m.  (10-13  ft.),  their  diameters  varying  between  20  and 
50  mm.  (f-2  inches).  The  general  principles  on  which  such 
apparatus  works,  leaving  out  of  consideration  special  types  for 
special  purposes,  are  practically  identical.  Every  evaporator 
should  be  equipped  with  an  accurate  thermometer  and  mercury 
vacuum-gauge,  as  well  as  properly  placed  sight-glasses,  as  well  as 
those  for  illumination,  so  that  the  interior  can  be  easily  inspected 
at  all  times. 

In  single-effect  apparatus  one  kilo  of  steam  will  evaporate 
an  equivalent  amount  of  water  at  the  usual  temperature  obtained, 
that  is  to  say,  a  kilo.  The  heat  of  the  steam  coming  from  the 
evaporator  can  be  further  utilized  by  using  it  over  again  for 
evaporating  or  heating  in  a  separate  vessel.  Our  consideration 
of  the  work  of  the  single-effect  apparatus,  which  we  will  now  take 
up,  will  not  have  to  do  with  steam-ecomony  only  so  far  as  to 
ascertain  under  what  conditions  the  greatest  possible  amount  of 
water  can  be  evaporated  based  on  this  unit  for  the  heating- 
surface,  and  under  what  conditions  it  is  at  its  maximum  efficiency 
without  being  subject  to  special  disadvantages. 

The  amount  of  heat  which  passes  through  the  heating  walls  in 


EVAPORATION.  133 

a  unit  of  time  is  directly  proportional  to  the  temperature  fall, 
i.e.,  to  the  difference  in  temperature  of  the  heating  vapors  and  the 
boiling  liquid,  and  also  to  the  conductivity  of  the  metal  of  the 
heating  wall.  It  is  inversely  proportional  to  the  thickness  of  the 
heating  wall  and  to  the  magnitude  of  a  certain  resistance  which 
opposes  the  conductivity. 

This  resistance  comes  from  stationary  liquid  films  on  each 
side  of  the  heating  surface  which  are  caused  by  the  adhesion  of 
the  water  and  liquors  to  the  heat  wall.  Hence  the  heat  does  not 
pass  directly  from  the  steam  into  the  metal,  but  first  into  the 
water  flowing  along  the  heating  surface  and  from  this  into  the  sta- 
tionary water  film  clinging  to  the  metal  and  thence  into  the 
metal.  On  the  liquor  side,  it  is  the  same,  only  reversed,  from  the 
metal,  the  heat  passes  through  the  stationary  fluid  film  before 
entering  the  moving  liquor. 

Since  the  conductivity  of  water  and  water  solutions  is  100  times 
smaller  than  that  of  iron  and  120  times  smaller  than  for  brass, 
it  is  obvious  that  stationary  films  of  exceeding  thinness  will  im- 
pede the  heat  transference  greatly.  „ 

Any  condition  influencing  the  thickness  of  this  motionless 
film  affects  the  heat  transference.  This  thickness  depends  on 
the  speed  of  movement  of  the  water  and  liquors  and  on  their 
viscosity,  the  latter  being  inversely  proportional  to  the  temper- 
ature of  the  liquid  and  directly  proportional  to  its  concentration. 
The  speed  of  movement  depends  on  the  construction  of 
the  evaporating  apparatus,  and  for  boiling  liquors  is  de- 
pendent besides  on  the  quantity  of  steam  bubbles  which  are 
given  off. 

Hence,  the  heat-transference  from  steam  to  the  boiling  liquid 
is  in  proportion  to: 

1.  The  speed  of  the  movement  of  the  liquor  over  the  heating- 
surface; 

2.  Inversely  as  the  height  of  liquor,  or  its  pressure,  on  the 
heating-surface ; 

3.  The  speed  with  which  the  steam  circulates  over  the  heating- 
surface  ; 


134  BEET  SUGAR  MANUFACTURE. 

4.  The  speed  and  thoroughness  with  which  the  condensed  water 
is  taken  away  from  the  heating-surface; 

5.  The    completeness    of    the    vacuum   in    the    evaporating- 
chamber. 

6.  The  conductivity  of  the  heating-surface,  that  is,  its  freedom 
from  scale  and  foreign  substance; 

7.  Inversely  as  the  viscosity  of  the  liquor; 

8.  The  temperature  of  the  liquor,  which  depends  upon  the 
pressure  under  which  it  boils. 

9.  The  magnitude  of  the  temperature-drop  between  the  steam 
and  the  boiling  liquor. 

These  conditions  for  good  heat -transference  should  be  attained 
in  the  simplest  possible  manner,  so  that  in  actual  practice  the 
construction  is  without  complication,  all  parts  are  capable  of  easy 
inspection,  and  the  apparatus  easy  to  run.  There  should  also 
be  security  against  juice  loss:  and  finally  the  evaporation  should 
not  be  too  expensive. 

In  short,  simplicity  in  construction  and  working  are  the  chief 
requisites  in  all  sugar-house  evaporators.  Since  evaporators 
work  night  and  day,  only  a  few  hours  on  Sunday  being  available  for 
cleaning  and  repairs,  all  parts  should  be  made  with  a  view  of 
avoiding  all  chance  of  interruptions  to  the  work  of  the  factory, 
especially  those  which  might  require  more  than  ordinary  care  and 
attention,  since  the  running  of  evaporators  must  usually  be  left  to 
unskilled  labor. 

This  requirement  of  simplicity  is  usually  met  in  a  very  satis- 
factory way  in  the  horizontal  and  vertical  apparatus  found  in 
most  factories.  With  other  types,  some  of  which  are  recom- 
mended on  quite  sound  theoretical  grounds,  such  as  the  film 
apparatus,  interruptions  and  irregularity  in  working  are  -con- 
tinual, so  that  properly  such  have  not  found  much  footing  in  the 
industry.  In  place  of  a  vertical-tube  system,  some  evaporators 
have  been  built  with  inclined  tubes  and  are  recommended  both 
for  evaporation  and  crystallization.  For  certain  purposes  they 
may  have  some  advantages,  but  it  has  not  appeared  that  they  are 


KVArORATIOX.  135 

any  more  efficient  than  a  properly  constructed  vertical 
apparatus. 

It  must  always  be  kept  in  mind  that  the  efficiency  of  an  evapo- 
rating apparatus  is  of  course  the  leading  consideration,  and  it  cer- 
tainly makes  no  difference  whether  you  pay  the  same  price  per 
square  foot  of  heating-surface  in  one  case  as  for  two  square  feet 
in  an  apparatus  of  different  make  of  only  half  the  efficiency. 
Indeed  the  efficiency  of  an  evaporating  apparatus,  speaking 
generally,  is  dependent  not  on  the  special  heat  economy  of  the 
whole  system,  but  entirely  on  the  proper  arrangement  and  combina- 
tion of  the  individual  parts. 

The  efficiency  of  a  single-effect  apparatus,  therefore,  does  not 
depend  primarily  on  any  special  design,  although  this  is  always  an 
important  consideration.  With  whatever  apparatus  is  at  hand, 
the  object  should  always  be  to  work  it  to  its  highest  efficiency. 
With  such  an  end  in  view,  excellent  results  can  be  obtained  with 
very  simple  means  and  costly  enlargements  of  the  evaporating- 
plant  be  avoided,  if  the  fundamental  requirements  for  the  case  at 
hand  are  thoroughly  understood.  A  brief  description  of  the 
means  of  increasing  the  efficiency  of  the  ordinary  vertical  and 
horizontal  evaporators  seems  therefore  necessary. 

The  most  important  influences  on  the  efficiency  of  an  evaporator 
are  the  juice-level  and  the  juice-circulation.  Formerly  it  wns 
thought  necesary  to  keepthe  juice-level  in  vertical  apparatus  at  least 
high  enough  to  fully  cover  the  upper  tube-plate,  so  that  the  liquor 
would  be  at  least  as  deep  as  the  tubes  were  long,  that  is,  1J-1} 
meters  (4-5  ft.).  It  was  the  same  in  the  ordinary  horizontal 
evaporators.  However,  the  deeper  the  juice-layer  which  rests  on 
the  heating-surface,  the  higher  proportionally  the  pressure  on  that 
part  of  the  heating-surface  and  consequently  the  boiling-point. 
The  fact  that  actual  experiments  with  thermometers  show  exactly 
the  same  temperatures  at  the  top  and  bottom  of  the  heating  sys- 
tem is  no  argument  against  this  statement,  since  the  movement  of 
the  liquor  m  the  apparatus  is  so  swift  that  juice  overheated  at  any 
part  of  the  heating-surface  directly  against  it  immediately  moves  on, 


1^6  BEET  SUGAR  MANUFACTURE. 

and,  after  giving  up  its  excess  of  heat,  mixes  in  with  the  common 
circulation,  so  that  the  temperature,  measured  by  introducing  a 
thermometer,  will  be  equal  at  all.  points.  Nevertheless  it  is  true 
that  liquor  next  to  the  heating-surface  under  a  head  of  juice,  as 
well  as  the  heating-surface  itself,  must  have  a  higher  temperature, 
if  bubbles  are  given  off  and  this  liquor  is  not  circulating  with  the 
rest.  Certainly  this  is  so  when  the  bubbles  are  escaping,  or  otherwise 
no  steam  could  be  formed.  The  difference  in  temperature  between 
the  steam  used  for  heating  and  that  of  the  liquor  which  is 
in  actual  contact  with  the  heating-surface  is  less,  therefore,  the 
greater  the  head  of  liquor.  Since  the  rate  of  evaporation  is  approx- 
imately proportional  to  the  temperature -fall,  it  follows  that  the 
efficiency  of  an  evaporating  apparatus  is  diminished  by  keeping 
the  juice  at  a  high  level.  On  this  account  the  heating-tubes  in 
vertical  apparatus  have  been  made  shorter,  but  with  the  disad 
vantage  that  the  heating-surface  Was  diminished,  since  for  other 
reasons  the  diameter  of  an  evaporator  should  not  exceed  3  meters 
(10  feet). 

Such  shortening  of  the  heating-tubes  is  not  only  unnecessary, 
but  indeed  detrimental  to  the  evaporating  efficiency  if  the  apparatus 
is  worked  at  a  low  juice-level.  The  juice  will  be  projected  out  of 
the  tubes  by  the  escaping  steam-bubbles,  and  will  rise  in  foam  so 
that  the  tubes  throughout  their  entire  length  will  be  covered  with 
liquor,  the  circulation  over  the  heating-surface  will  be  rapid,  and 
in  consequence  of  the  foam  only  a  slight  pressure  will  be  exerted 
by  the  bubbles.  The  longer  the  heating-surfaces  are,  up  to  a 
certain  limit,  the  more  rapid  the  juice-circulation  without  marked 
increase  of  pressure  in  the  lower  part  and  the  greater  the  efficiency 
of  the  heating-surface. 

How  low  the  juice-level  should  be  carried,  as  shown  by  a  juice- 
gauge  working  according  to  the  principle  of  communicating  tubes, 
depends  on  many  conditions,  especially  on  the  viscosity  of  the 
liquor  and  the  volume  .of  the  steam-bubbles  formed  from  a  specified 
quantity  of  water.  In  the  last  effect  containing  concentrated  liquor, 
therefore,  the  level  can  be  maintained  lower  than  with  thin  juice. 
Experience  teaches  the  proper  height,  but  care  should  be  taken  to 
have  the  juice  always  foaming  or  spurting  out  of  all  heating-tubes. 


EVAIORATIOX.  137 

In  the  horizontal  apparatus,  also,  the  juice-level  should  be  as 
low  as  possible,  although  these  will  not  work  as  satisfactorily  as 
the  vertical.  Nevertheless  it  is  possible  with  horizontal  makes 
to  get  a  very  large  heating-surface  with  small  height  of  steam-chest 
if  the  trunk  shape  ("wagon-top")  design  is  used.  This  form  is 
therefore  the  best  of  all. 

In  order  to  increase  and  facilitate  the  juice-circulation  of 
vertical  evaporators,  circulation-tubes  of  large  diameter  are  placed 
in  the  middle  or  distributed  through  the  heating-surface,  these 
serving  to  return  the  juice  coming  out  of  the  top  of  the  tubes  down 
to  the  bottom  of  the  apparatus.  Often  the  juice  flows  back  at  the 
outer  edge  of  the  tube  system,  this  being  so  suspended  as  to  form 
a  ring-space  between  the  walls  of  the  evaporator  and  the  tube 
section.  In  the  horizontal  evaporators  the  single  tubes  or  tube 
sections  should  be  sufficiently  far  apart  to  allow  the  juice  to  find 
its  way  to  the  bottom  readily. 

Another  way  to  increase  the  speed-circulation  of  juice  consists 
in  hanging  wooden  or  enamelled  iron  rods  in  the  heating- tubes  so 
that  their  circular  section  is  contracted  to  a  ring.  The  trouble  with 
using  wooden  rods  is  that  they  become  disintegrated  through  action 
of  the  heat  and  the  alkalies  in  the  juice,  while  after  boiling  out  the 
apparatus  with  acid  they  color  the  juice  dark.  Iron  rods  in 
proportion  to  their  usefulness  are  too  expensive. 

The  speed  of  the  juice-circulation  can  also  be  increased  by  using 
tubes  of  smaller  diameter,  because  the  capacity  of  a  tube  decreases 
much  faster  than  its  heating-surface.  Usually  narrower  tubes  are 
used  for  the  first  effect  than  for  the  last,  so  as  to  have  the  diameter 
of  the  heating-tubes  bear  a  certain  relation  to  the  volume  of  the 
escaping  steam. 

A  contrivance  for  improving  the  juice-circulation  in  the  first 
effect  of  a  multiple-effect  apparatus  is  called  the  "circulator"  and 
consists  of  a  small  vertical  evaporating  apparatus  connected  with 
the  regular  thin-juice  effect  above  and  below.  The  circulator  is 
heated  with  direct  steam,  which  throws  up  the  juice  in  bubbles  and 
forces  it  over  into  the  tube  system  of  the  large  apparatus,  while  the 
juice  in  the  bottom  of  the  large  effect  passes  into  the  small  apparatus. 


138  BEET-SUGAR  MANUFACTURE. 

The  use  of  this  circulator  is  very  doubtful,  because  the  circulation 
induced  by  it  in  the  large  apparatus  is  one  which  already  exists 
there,  but  in  exactly  the  reverse  direction.  If  the  circulator  is 
advantageous,  it  is  because  it  utilizes  the  high  temperature  of 
direct  steam,  better  than  by  mixing  live  steam  with  exhaust 
whose  temperature  and  pressure  make  it  useless  for  expansion. 
Hence  in  the  circulator  the  temperature  fall  is  very  much  greater 
than  in  the  first  effect,  with  which  it  is  connected  and  its  capacity 
per  unit  of  heating  surface  likewise  greater. 

The  heat-transference  depends  also  upon  the  speed  with  which 
the  steam  passes  over  the  heating-surface  and  upon  the  readiness 
with  which  condensed  water  is  taken  away  from  the  heating- 
surface.  In  vertical  apparatus  the  speed  of  the  steam  in  the  heating 
chambers  is  not  great,  whereas  the  condensed  water  flows  away  from 
the  vertical  tubes  quickly  and  completely.  In  horizontal  apparatus 
a  great  speed  can  be  obtained  by  a  suitable  arrangement  of  the 
heating-tubes  in  sections,  especially  if  the  tubes  have  a  small 
diameter,  only  20  mm.  (f  inch)  or  less.  The  speed  is  only  very 
great,  however,  in  the  region  adjacent  to  the  steam-entrance;  as 
the  steam  goes  toward  the  condensation  discharge-pipe  its  velocity 
lessens  till  it  finally  becomes  practically  zero.  The  condensed 
water  flows  but  slowly  in  the  tubes  of  the  horizontal  apparatus;  in 
fact  the  lower  parts  will  never  be  quite  free  from  water  unless  it 
collects  in  places  where  the  flow  of  the  steam-current  is  swift,  so 
that  the  water  is  carried  along  with  it.  Vertical  apparatus  should 
be  improved  so  as  to  increase  the  steam-flow,  while  in  horizontal 
apparatus  the  aim  should  be  to  carry  away  the  water. 

All  steam,  direct  as  well  as  exhaust,  carries  a  small  amount 
of  uncondcnsed  gases,  especially  air,  small  quantities  of  carbon 
dioxide,  and  ammonia.  Usually  these  condensed  gases  are  re- 
ferred to  as  "  ammonia-vapor/'  although  the  bulk  of  the  ammonia 
is  absorbed  by  the  condenser  water.  If  these  gases  are  not  taken 
away,  they  collect  in  the  heating-chambers  and  take  up  a  constantly 
increasing  space,  which  is  consequently  lost  for  condensation  and 
likewise  for  heat-transference;  hence  the  importance  of  completely 
and  continually  removing  these  gases  is  obvious,  and  the  more 


EVAPORATION.  159 

so  when  it  is  remembered  that  the  ammonia  always  present  in 
combination  with  the  oxygen  of  the  air  corrodes  brass  and  copper 
tubes  badly  if  allowed  to  remain  long  in  one  place.  Attempts 
have  been  made  to  remove  the  ammonia  collecting  in  the  exhaust- 
steam  piping,  by  means  of  sulphurous  acid,  sulphuric  acid,  potash 
alum,  or  other  absorbing  agent,  with  the  hope  of  getting  back  the 
increased  expense  by  the  value  of  the  ammonia  recovered;  but 
these  contrivances  have  not  proved  economical.  The  amount 
of  ammonia  in  the  exhaust-steam  has  been  greatly  overesti- 
mated. 

In  the  evaporation  of  the  juice  of  100  kg.  (220  Ibs.)  of  beets  from 
20  to  30  grams  (about  an  ounce)  of  ammonia  has  been  obtained 
under  favorable  conditions,  so  that  in  a  factory  of  average  capacity 
there  would  be  recovered  daily  only  from  100  to  200  kg.  (220-440  Ibs.) 
of  ammonia  gas.  This  small  amount  does  not  pay  for  the  costly 
and  unreliable  apparatus  which  would  have  to  be  built  into  each 
effect  of  the  evaporator.  Moreover,  such  apparatus  would  only 
mitigate  the  corrosion,  since  gases  other  than  ammonia  still  remain 
in  the  steam  to  be  sucked  off.  Such  a  gas  is  carbon  dioxide,  which 
originates  in  the  juice  and  which  escapes  in  large  quantities, 
especially  from  over-carbonatated  liquors.  Frequently  this  gas 
forms  ammonium  carbonate  with  the  ammonia  in  such  quanti- 
ties as  sometimes  to  stop  up  small  pipes. 

Naturally  a  large  escape  of  gas  does  not  occur  when  the  steam 
passes  into  the  heating-chambers,  where  there  is  always  a  strong 
current  but  there  are  spaces  where  this  current  is  quite  slow,  and 
it  is  there  that  the  gas  collects.  Experience  has  shown  that  in 
vertical  apparatus  only  the  upper  ends  of  the  brass  tubes  are 
corroded,  from  which  it  has  been  correctly  inferred  that  the  gas 
collects  only  in  the  top  of  the  heating-chamber.  Vent-pipes  are 
therefore  placed  in  the  top  tube-plate,  arranged  in  different  places 
according  to  the  number  and  position  of  the  steam-inlets.  If 
there  is  only  one  steam-inlet,  the  pipe  is  located  where  it  can 
exhaust  most  efficiently,  that  is,  where  the  uncondensable  gases 
contain  least  steam,  at  a  point  farthest  from  the  outer  edge  and 
the  middle  circulation-pipe.  If  there  are  two  steam-entrances  on 


140  BEET-SUGAR  MANUFACTURE. 

opposite  sides,  then  the  place  to  vent  is  half-way  between  them. 
Should  experience  show  that  there  was  corrosion  at  other  points, 
vents  must  be  put  in  at  such  places  also,  for  these  corroded  spots 
are  unmistakable  signs  of  a  collection  of  gas.  In  placing  vent- 
pipes  in  the  tube-plate  care  must  be  taken  not  to  let  them  project 
through  the  tube-plate,  but  to  cut  them  off  flush  with  the  under 
side,  otherwise  there  will  be  a  collecting-space  which  cannot  be 
exhausted  of  gas.  In  order  to  prevent  corrosion  of  the  upper 
part  of  the  tubes  entirely  it  is  also  suggested  that  they  be  coated 
with  a  durable  varnish  or  specially  protected  in  some  similar  way. 

In  the  horizontal  evaporators  the  steam-entrance  is  always  at 
one  end;  in  consequence  the  uncondensable  gases  will  be  forced  to 
the  exit  ends  of  the  tubes  or  into  the  tube-chest,  together  with 
the  condensed  water.  The  vents  should  therefore  be  at  the  top 
of  the  exit-chamber.  If  the  tubes  are  not  perfectly  horizontal 
but  bent,  the  gas  will  collect  in  these  bent  tubes  and  corrode  them 
in  a  short  time. 

As  already  mentioned,  it  is  impossible  to  remove  only  gas;  a 
comparatively  large  quantity  of  steam  escapes  at  the  same  time. 
Just  how  far  gas- venting  should  be  carried  can  be  determined  only 
by  actual  experience.  A  little  too  much  is  better  than  not  enough, 
for  the  steam-loss  is  not  so  serious  as  a  bad  corrosion  of  the  tubes 
and  consequent  wearing  out  of  apparatus.  Most  care  should  be 
given  to  the  venting  of  the  heating-chamber  of  the  first  effect, 
because  here  the  steam  is  at  its  greatest  efficiency;  the  vapors  in 
the  later  effects,  which  have  been  used  over  several  times,  have 
less  pressure,  so  that  the  gases  can  be  drawn  off  freely,  opening  the 
cocks  fairly  wide.  As  a  limit  it  may  be  stated  that  the  vent- 
valves  or  cocks  of  the  first  effect  should  not  have  an  opening 
of  more  than  5  or  10  mm.  (^-J  inch).  If  they  happen  to  be 
larger,  their  openings  should  be  reduced,  or  a  diaphragm  with 
a  hole  of  the  appropriate  size  screwed  into  the  pipe.  On  the  other 
hand,  the  valves  of  the  last  effects  can  have  a  diameter  of  25-50 
mm.  (1-2  in.)  and  should  be  at  least  half  open.  In  order  to  keep 
the  heat-loss  within  reasonable  limits,  the  steam  which  is  taken 
off  and  which  contains  less  than  \%  of  uncondensable  gas  is  not 


i;\ '.\:\  RATION.  141 

led  to  the  condenser  but  to  the  evaporat ing-chamber  of  the  same 
effect,  so  that  the  steam  is  used  in  the  next  effect. 

It  should  be  seen  that  a  rapid  and  complete  exhaustion  in  the 
evaporator  can  be  obtained  at  the  time  it  is  started,  when  the 
heating-chambers  are  full  of  air. 

Before  the  heat  of  the  steam  can  act  on  the  liquor  it  must 
first  pass  the  walls  of  the  heating-surface.  The  material  used  for 
the  tubes  is  usually  brass,  iron,  or  steel;  copper  is  little  used  for 
evaporators,  except  in  the  coils  of  vacuum-pans.  The  conductivity 
of  metals  varies  considerably,  although  this  difference  is  of  little 
consequence  if  the  heating-surfaces  of  the  tubes  are  clean.  More 
depends  on  the  thickness  of  the  walls,  especially  as  the  walls 
of  an  iron  tube,  which  is  a  poorer  conductor,  must  be  thicker  than 
those  of  a  brass  tube.  A  very  important  point  is  the  condition  of 
the  heating-surface,  not  only  on  the  juice  side,  but  the  steam  side 
also.  The  most  important  consideration  which  makes  brass  tubes 
better  than  those  of  iron  is  that  the  iron  after  a  short  time  becomes 
covered  with  a  thin  coating  of  rust  which  cannot  be  removed  and 
conducts  heat  badly.  Iron  tubes  with  especially  thin  walls  have 
been  used  in  many  factories,  but  these  thin-walled  tubes  are  not 
to  be  recommended,  because  they  are  attacked  when  the  apparatus 
is  boiled  out  with  muriatic  acid  and  soon  must  be  renewed  because 
of  leaks.  On  the  juice  side  the  sole  problem  with  tubes  of  all 
kinds  is  that  of  scale-deposit. 

There  are  indeed  few  cases  of  thin  juices  which  do  not  deposit 
scale  however  well  filtered  and  defecated.  The  salts  which  are  the 
chief  scale  formers,  namely,  those  of  limp  with  carbonic,  sulphuric, 
sulphurous,  oxalic,  and  some  organic  acids,  are  but  partly  soluble 
in  the  thin  juice.  Being  more  soluble  in  thin  juice  they  precipi- 
tate, not  only  from  the  evaporation  but  also  on  account  of  their 
slight  solubility  in  the  thickened  juice,  and  form  a  firm  coating  0:1 
the  heating-surfaces.  If  the  thickness  of  the  scale  keeps  within 
moderate  limits,  the  evaporating  efficiency  of  the  apparatus  does 
not  suffer  appreciably,  but  in  the  course  of  time  the  amount  of 
deposit  becomes  so  great  that  measures  must  be  taken  to  remove  it. 

The  amount  of  deposit  varies  greatly  in  the  different  vessels 


142  BEET  SUGAR  MANUFACTURE. 

of  a  multiple-effect  apparatus.  If  the  juice  is  well  defecated, 
carbonatated,  filtered,  and  boiled  up,  very  little  deposit  is  found 
in  the  first  effect,  but  in  the  later  effects  there  will  be  more  or  less 
according  to  the  content  of  difficultly  soluble  lime  salts.  If  the 
final  carbonatation  is  incomplete  or  not  carried  out  hot  enough, 
or  the  filtration  carelessly  done,  a  thick  scale  will  appear  in  the 
first  effect.  This  deposit  consists  mostly  of  little  slime-particles 
which  get  into  the  apparatus,  the  deposits  in  the  later  effects  being 
caused  by  the  precipitation  of  the  lime  salts  dissolved  in  the  thin 
liquors  through  their  concentration.  Hence  boiling  up  the  juice 
before  evaporating  will  not  prevent  the  formation  of  these  deposits 
in  the  later  effects.  Boiling  up  of  the  juice  before  and  after  final 
carbonatation  is  so  effective  that  there  is  little  use  for  a  special 
blow-up  plant  for  thin  liquor  which  has  been  properly  carbonatated 
and  filtered,  as  experience  has  often  shown  in  those  places  where 
work  goes  on  without  Sunday  intermissions.  What  seems  more 
advisable  in  such  cases  is  introducing  a  filter-plant  for  the  juice 
passing  from  one  effect  to  the  next,  in  some  cases  using  pumps  if 
the  difference  in  pressure  is  too  small. 

Removal  of  scale  by  mechanical  means,  such  as  brushes,  scrapers, 
or  cutters,  is  only  possible  in  vertical  evaporators  during  crop 
time:  not  in  the  horizontal  ones,  because  their  tubes  have  to  be 
removed  for  this  purpose.  Indeed  mechanical  cleaning  of  vertical 
apparatus  is  difficult,  slow,  and  laborious.  Hence  chemical  clean- 
ing is  practiced  everywhere,  either  boiling  out  with  soda  and  then 
with  muriatic  acid  or  with  acid  alone,  which  with  rare  exceptions, 
providing  the  boiling  is  thoroughly  done  every  Sunday,  keeps  up 
the  efficiency  of  the  apparatus  throughout  the  crop. 

If  the  scale-deposit  is  practically  all  carbonate  of  lime,  boiling 
with  muriatic  acid  is  sufficient.  Often,  however,  there  are  other 
lime  salts  present  which  form  deposits  not  readily  soluble  in 
muriatic  acid,  more  particularly  lime  salts  of  sulphurous,  sulphuric, 
or  oxalic  acid;  likewise  lime  soaps  which  are  formed  from  fats 
introduced  to  prevent  foaming.  Other  occasional  constituents  of 
scale  are  silicic  acid,  alumina,  and  iron  oxide,  which  come  from  the 
lime;  likewise  undecomposed  fats,  which  do  harm  so  far  as  they 


EVAPORATION.  143 

prevent  disintegration  of  the  scale  by  the  boiling  liquors  and 
therefore  impede  the  action  of  the  muriatic  acid.  In  all  such  cases 
it  is  advisable  to  boil  with  dilute  soda  solution  first,  so  as  to  change 
lime  salts  into  carbonate  and  disintegrate  the  scale  by  dissolving 
the  free  fats.  The  scale  so  treated  dissolves  easily  in  muriatic  acid. 
If  it  is  desirable  to  dispense  with  a  double  boiling  out,  a  charge 
of  sodium  bisulphite  (acid  sulphite)  is  excellent,  as  this  changes 
the  lime  carbonates  and  organic  salts  into  sulphites  which  expand 
and  so  crack  and  break  up  the  hard  scale  that  it  i.s  readily  attacked 
by  the  muriatic  acid.  Rarely  scale  resists  this  treatment,  unless 
it  contains  a  large  amount  of  silica  and  alumina,  when  mechanical 
means  must  be  resorted  to. 

Muriatic  acid  used  for  cleaning  evaporators  must  not  be  too 
concentrated,  as  it  should  under  no  circumstances  dissolve  any 
appreciable  amount  of  iron  which  would  weaken  the  apparatus. 
The  scale  makes  sufficient  protection  to  the  walls  of  the  apparatus 
if  dilute  acid  is  used.  The  amount  of  hydrochloric  acid  in  the  acid 
water  should  never  be  more  than  1%  for  the  last  effect  where  the 
scale  is  most,  and  not  more  than  }-£  per  cent,  in  the  preceding 
effects.  To  prevent  the  walls  from  being  attacked  by  the  muriatic 
acid  as  it  enters,  as  might  easily  happen  if  it  is  too  concentrated, 
it  is  a  good  idea  to  draw  it  into  the  apparatus  while  the  water  is 
boiling  under  vacuum  by  means  of  a  pipe  extending  into  the 
middle,  as  when  the  water  is  boiling  the  mixture  will  be  immediate 
The  boiling  should  not  be  at  too  high  a  temperature  and  should 
last  1-2  hours.  If  the  work  is  done  in  that  way,  the  apparatus 
is  brought  to  its  original  efficiency,  it  is  in  nowise  injured,  and 
should  be  good  for  twenty  years'  work,  or  more. 

While  boiling  out  with  acid,  acidity  tests  of  the  condensation- 
water  should  be  taken.  If  it  reacts  acid,  it  should  not  be  used 
for  boiler-feed,  or  it  should  be  first  neutralized  with  soda. 

The  soda  solution  used  for  boiling  out  should  contain  J  to  1J  per 
cent,  of  anhydrous  sodium  carbonate.  Boiling  out  with  this  solu- 
tion should  be  as  long  as  possible,  and  the  highest  possible  tempera- 
ture should  be  maintained  in  all  effects.  The  vacuum  is  therefore 
lowered  by  opening  the  air- valves,  or  most  of  the  water  is  turned 


144  BEET-SUGAR    MANUFACTURE. 

off  the  condenser.  Violent  boiling  is  not  necessary  here,  as  is  the 
case  when  muriatic  acid  is  used.  It  is  sufficient  if  the  liquor  is 
merely  moving. 

After  boiling  out  with  muriatic  acid,  the  evaporator  is  imme- 
diately emptied  of  acid  water  and  very  carefully  washed  out  with 
pure  water,  the  best  way  being  to  fill  up  over  the  tubes.  All  water 
connections  of  the  evaporator  should  come  from  a  common  pipe 
closed  by  one  main  valve.  This  valve  is  securely  locked  when  the 
apparatus  is  running,  so  that  no  water  can  mix  with  juice  through 
any  misuse  of  it.  No  inspection  of  the  apparatus  should  be  made 
after  it  has  been  boiled  out  till  sufficient  air  has  been  sucked  in 
by  the  vacuum-pump  to  insure  against  any  possible  danger  from 
detonating  gas  being  inside. 

If  the  full  efficiency  is  not  restored  after  boiling  out,  it  is  a  sign 
that  the  solutions  were  too  weak  or  that  the  boiling  out  was  not 
long  enough.  This  will  have  to  be  rectified  the  following  Sunday. 
It  is  not,  however,  necessary  that  the  tubes  be  completely  clean 
and  free  from  scale  after  boiling  out,  as  long  as  the  evaporation  is 
as  good  as  ever,  and  the  scale-deposit  thinner,  and  especially  if  it 
has  Become  porous.  It  is  obvious  that  all  apparatus  must  be 
fitted  with  suitable  valves  for  introducing  chemicals  and  boiling 
them  up  quickly.  Everything  should  be  arranged  as  conveniently 
as  possible  for  utilizing  to  best  advantage  the  short  resting- time 
which  Sunday  affords. 

The  viscosity  of  the  juice  exerts  another  most  important  in- 
fluence on  the  heat-transference  in  evaporators.  Since  the  juice 
has  a  purity  of  90  or  more,  there  are  but  little  non-sugars  in  pro- 
portion to  the  sucrose,  and  their  influence  is  so  small  that  the 
variable  constitution  of  the  juice  need  not  be  taken  into  considera- 
tion. Juices  of  the  same  concentration  have  practically  the  same 
viscosity,  but  this  viscosity  increases  enormously  in  proportion 
to  the  concentration  of  the  juice,  that  is  with  its  sugar-content. 
Hence  thickened  juices  are  much  more  viscous  than  thin  ones 
and  make  the  capacity  of  the  thick-juice  effects  notably  less  than 
that  of  the  thin-juice  effects. 

Moreover,  the  last  effects  work  under  more  unfavorable  condi- 
tions in  one  other  point,  namely,  that,  owing  to  the  higher  vacuum, 


EVAPORATION.  145 

they  have  a  lower  boiling-temperature  than  the  first  effect.  The 
heat-transference  is  less  at  a  lower  temperature  than  at  a  higher, 
all  other  conditions  being  equal,  and  this  heat-coefficient  falls 
rapidly  at  temperatures  below  the  boiling-point,  while  at  100° 
or  over  the  change  is  not  so  great.  It  would  be  more  advantageous, 
therefore,  from  this  point  of  view,  to  have  all  the  effects  evaporate 
at  a  temperature  of  about  100°  or  over.  The  highest  pressure  of 
engine  exhaust-steam  is,  however,  under  usual  conditions  J-l 
atmosphere  (12-15  Ibs.),  hence  its  temperature  is  as  high  as  115°- 
120°  (239°-248°  F.),  which  gives  too  small  a  range  for  the  entire 
temperature-drop  necessary  for  a  multiple  effect.  Aside  from  this, 
the  thicker  sirups  must  be  evaporated  at  the  lowest  possible 
temperature  to  avoid  decomposition. 

As  a  preventive  of  the  injurious  influence  of  the  unavoid- 
ably low  boiling-temperature  in  the  last  effects,  resort  is  made 
to  an  increase  in  temperature-fall  in  the  effects  boiling  under  a 
vacuum.  By  increasing  this  fall  not  only  is  the  amount  of  heat 
transferred  corresponding  to  this  fall  greater,  but  the  heat-trans- 
ference coefficient  rises  proportionally.  This  coefficient,  that  is 
the  amount  of  heat  transferred  to  one  square  meter  of  heating- 
surface  in  one  hour  for  every  degree  centigrade,  is  about  10  for 
a  temperature-fall  from  75°  to  65°,  but  for  a  fall  from  85°  to  65° 
it  is  about  15.  In  practice,  therefore,  use  must  be  made  of  this 
fact. 

There  should  be  no  mechanical  sugar-loss  in  a  properly  con- 
structed evaporating  apparatus.  The  only  cause  for  such  loss  is  in 
leaks  in  tubes  or  tube-plates.  While  running  no  loss  of  juice  can 
commonly  occur  here,  as  the  pressure  of  the  steam  in  the  heating- 
chamber  is  obviously  always  greater  than  in  the  evaporating  section, 
including  the  pressure  of  the  juice-column.  Indeed  steam  and 
condensed  water  can  enter  the  juice  at  any  leaky  spot,  but  the 
juice  can  never  enter  the  steam-space.  When  work  is  interrupted 
the  conditions  become  quite  different,  and  thin  juice  loss  is 
the  unavoidable  consequence  of  such  leaks.  Therefore  great 
care  should  be  taken  to  keep  the  tubes  in  good  condition  and 
the  tube-plates  tight.  Before  the  campaign,  the  apparatus  when 


146  BEET  SUGAR  MANUFACTURE. 

ready  to  start  should  be  tested  by  water-pressure,  and  especially 
the  multiple  effects,  using  the  water-tank  pressure  which  is 
always  more  than  1  atmosphere  (15  Ibs.)  and  putting  on  the 
juice-boiler  a  pressure  higher  than  the  highest  steam-pressure  used. 
In  vertical  apparatus  the  water-pressure  should  be  on  the  steam- 
chamber,  in  the  horizontal  evaporators  on  the  juice  side,  so  that 
every  tube  will  be  tested  for  leaks. 

The  second  cause  of  sugar-loss  is  entrainment  of  juice-spray  in 
the  exit-vapors.  In  this  way  much  loss  can  take  place  if  unfavorable 
conditions  exist.  Entrainment  of  juice  is  more  likely  the  greater 
the  evolution  of  steam  from  the  juice,  the  more  energetic  the 
escape  of  bubbles  from  the  surface  of  the  liquor,  the  higher  the 
viscosity,  and  the  more  rapid  the  current  of  vapors  passing  out  of 
the  apparatus. 

In  the  first  effect,  danger  of  entrainment  is  very  small  because 
when  under  pressure  or  light  vacuum  the  escaping  steam  has  little 
A^olume,  while  the  juice  is  thin  and  mobile  and  the  vapor-current 
slow.  In  the  later  effects,  on  the  contrary,  where  the  steam  has 
nearly  six  times  the  volume  it  has  under  atmospheric  pressure, 
the  viscous  sirup  is  more  or  less  atomized  by  the  exploding  bubbles. 
This  escaping  spray  goes  through  the  tubes  where  the  speed  of  the 
vapor-current  is  100  meters  (328  ft.),  or  more,  a  second  and  is 
entrained  into  the  condenser  and  lost  in  the  hot-well. 

Juice-catchers  made  in  various  ways  are  placed  in  the  vapor- 
pipe  lines  for  trapping  this  juice-spray,  the  common  principle  on 
which  they  work  being  to  retain  the  minute  drops  of  liquor  either 
on  the  surfaces  of  sieves  or  vertical  partitions,  or  to  allow  them  to 
fall  into  an  enlarged  chamber  in  the  pipe.  The  value  of  these 
juice-traps  is  often  doubtful.  They  can  do  harm  if  the  juice 
which  is  caught  does  not  flow  back  at  once  into  the  evaporator. 
This  juice,  which  is  much  diluted  by  the  condensed  water,  cools 
and  becomes  a  breeding  place  for  micro-organisms  which  quickly 
propagate  in  great  quantities.  If  this  badly  infected  juice  flows 
into  a  thick  juice  effect,  the  bacteria  will  continue  to  propagate 
if  the  vacuum  is  high,  since  the  temperature  will  be  low.  The 
temperature  of  the  thick  juice  effects  never  is  high  enough  to 


EVAPORATION.  147 

trouble  bacteria.  Hence  the  thickened  juice  is  infected  with 
living  germs  which  readily  pass  over  into  the  product  later  in 
process  unless  the  juice  is  subsequently  filtered  and  heated  suf- 
ficiently long  at  100°  C.  The  best  juice-trap  is  a  lofty  evap- 
ora  ting-chamber.  Two  opposing  forces  are  continuously  at  work 
upon  the  spray  thrown  off  from  the  surface  of  the  boiling  juice. 
The  initial  velocity  with  which  this  spray  is  hurled  upward,  either 
directly  or  obliquely,  is  augmented  by  the  upward  current  of  the 
vapor,  but  it  is  also  continually  diminished  by  the  influence  of 
gravity.  [In  the  broad  space  of  the  evaporating-chamber  the 
speed  of  the  steam-current  is  only  about  4-5  meters  (13-16.5  ft.)  a 
second,  about  equal  to  the  velocity  of  a  moderate  breeze.  At  such 
speed  there  is  little  tendency  for  the  thin  liquor  to  spurt  up,  but 
the  restraining  force  of  gravity  is  the  same  whether  the  drops  of 
liquor  are  large  or  small.  Experience  has  shown  that  the  vapor- 
space  of  the  evaporator  should  extend  from  3  to  5  meters  (10  to  16.5 
ft.)  above  the  juice-level  in  order  to  have  the  smallest  particles  of 
spray  lose  their  upward  velocity.  If  this  be  done,  there  need  be 
little  fear  of  sugar-loss  even  in  the  thick-sirup  effects. 

There  is  a  common  belief  that  it  is  not  the  drops  which  are 
entrained,  but  bubbles  consisting  of  thin  films  filled  with  vapor. 
Naturally  bubbles  of  this  nature,  owing  to  their  slight  density  and 
relatively  large  volume,  would  readily  be  entrained,  but  for  this 
bubble  hypothesis  there  is  no  good  scientific  reason,  and  scarcely 
any  actual  evidence.  It  is  certainly  a  fact  that  no  juice,  or,  if  any, 
a  quite  negligible  quantity,  is  e'ntrained  if  the  vapor-spaces  are 
sufficiently  high,  as  can  be  easily  proved  by  testing  the  water  in 
the  hot-well  for  sugar.  A  good  and  convenient  control  apparatus 
for  determining  whether  sugar  is  entrained  consists  of  a  trap  on 
the  bottom  of  any  horizontal  section  of  the  vapor-pipe.  A  small 
portion  of  any  sirup  entrained  will  deposit  with  the  water  condensed 
on  the  walls  of  the  pipe  and  will  flow  into  the  trap.  Naturally 
this  will  only  show  that  sugar-loss  sometimes  occurs,  but  if  the 
water  in  the  trap  shows  no  sugar,  or  only  a  trace,  it  can  be 
assumed  with  confidence  that  any  sugar-loss  must  be  exceed- 
ingly small. 


148  BEET-SUGAR  MANUFACTURE. 

Multiple-effect  Evaporating  Apparatus. — In  constructing  single 
effects  the  principal  considerations  are  reliability  of  working  and 
speedy  and  efficient  evaporation,  but  the  peculiar  arrangement  of 
the  evaporating  system  of  the  multiple  effect  has  the  additional 
object  of  more  complete  economy  of  the  heat  of  exhaust  and  direct 
steam  by  using  it  over  a  number  of  times  for  evaporating,  heating, 
and  boiling. 

The  number  of  effects  united  in  one  system  shows  the  number 
of  times  the  heat  of  the  steam  is  utilized,  although  occasionally 
two  or  more  evaporating-vessels  will  be  heated  with  steam  at  the 
same  pressure.  In  the  latter  case  such  vessels  can  be  considered 
as  one  member  of  the  multiple-effect  apparatus.  In  such  arrange- 
ments it  is  better  not  to  introduce  the  vapor  and  the  juice  directly 
into  each  vessel,  but  to  unite  th%  vessels  in  such  a  way  that  the 
juice  from  the  preceding  effect  enters  one  of  them  and  passes  out 
through  a  large  overflow  pipe  into  the  bottom  of  the  next,  the 
vapors  going  in  the  reverse  direction.  By  this  arrangement 
greater  efficiency  and  easier  control  are  effected,  since,  by  regulat- 
ing the  juice-level  in  the  first  vessel,  the  juice-level  of  the  other 
is  adjusted. 

There  are  certain  limits  to  the  use  of  steam  in  multiple  ef- 
fects. The  total  temperature-fall,  that  is  the  difference  be- 
tween the  temperature  of  the  steam  used  to  heat  the  first  ef- 
fect (exhaust-steam)  and  the  temperature  of  the  boiling  sirup 
in  the  last  effect,  is  at  most  50°  (122°  F.),  since  the  exhaust- 
steam  when  engines  are  working  economically  (and  if  they  do  not, 
the  work  suffers)  is  at  never  more  than  £  of  an  atmosphere  (11  Ibs.), 
while  the  vacuum  is  rarely  higher  than  60  cm.  (23.6  inches).  This 
total  temperature-drop  cannot,  however,  be  divided  into  any 
desired  number  of  smaller  temperature  changes,  but  rather  a  lower 
limit  of  fall  is  set  for  each  effect  below  which  a  good  evapora- 
tion cannot  be  obtained  even  by  increasing  the  heating-surface. 
Practical  experience  teaches  that  the  temperature-fall  in  the  first 
effect,  whose  contents  are  boiling  at  100°  or  over,  should  not  be  under 
4°-5°,  in  the  middle  effects  7°-10°,  and  in  the  last  effect  not  less  than 
15°.  Hence  it  follows  that  division  of  the  total  temperature-fall  into 


1YYPORATIOX.  149 

more  than  six  parts  is  not  practically  feasible,  and  hence  sextuple 
effects  represent  the  highest  limit  of  multiplication  used  in  sugar- 
manufacture.  But  since  there  are  also  great  difficulties  arising  in  the 
sextuple  use  of  exhaust-steam,  even-  quintuple  effects  have  not  be- 
come common  in  factories,  quadruples  being  mostly  used,  although 
many  triples  aiv  employed,  either  with  or  without  juice-heaters. 

If  the  amount  of  steam  which  an  evaporator  will  use  for  boil- 
ing and  heating  is  estimated,  it  should  be  on  the  assumption 
that  all  the  vapor  from  one  effect  of  an  evaporating  system  passes 
into  the  next  effect  and  is  condensed,  all  its  available  heat  being 
transferred  through  the  heating-walls  into  the  juice  and  being 
utilized  in  evaporation. 

One  kilogram  of  steam  on  condensing  gives  out  different  amounts 
of  heat  according  to  the  temperature  of  the  condensed  water.  If 
the  cooling  which  the  condensed  water  undergoes  when  flowing  away 
from  the  heating-tubes  is  taken  into  consideration,  and  this  differs 
according  to  the  construction  of  the  heating-tubes,  but  is  never 
very  great,  it  will  be  found  that  this  water  has  a  temperature  which 
will  cause  it  to  boil  under  the  vacuum  of  the  heating-chamber. 
Therefore,  the  higher  the  pressure  of  the  heating  vapors,  the  greater 
the  amount  of  heat  that  the  condensation-water  will  retain.  Hence 
in  a  single  effect  not  1  kg.  of  water  is  evaporated  by  1  kg,  of  steam, 
but  somewhat  less,  and  likewise  a  multiple-effect  evaporator  does 
not  evaporate  2,  3,  4,  or  more  kg.  out  of  the  juice,  but  always  less, 
in  proportion  to  the  excess  of  heat  of  the  condensed  water  over 
that  of  the  boiling  juice.  This  quantity  of  heat  is,  however,  so 
small  as  to  be  negligible  in  practical  work. 

If  there  is  approximately  the  same  quantity  of  water  to  be 
evaporated  out  of  the  juice  in  each  effect,  all  the  heating-surfaces 
should  not  be  equally  large,  since  the  magnitude  of  the  heat-trans- 
ference in  different  effects  is  very  different.  As  has  been  already 
shown  above,  the  conditions  for  heat-transference  are  much  more 
unfavorable  in  the  last  effect  than  in  the  first.  In  the  last  effects 
the  sirup  has  more  viscosity,  the  boiling-temperature  is  lower,  and 
the  deposit  of  scale  greater.  In  order  to  attain  the  greatest  possible 
efficiency  of  the  whole  evaporating'  system,  these  unalterable, 


150  BEET  SUGAR  MANUFACTURE. 

unfavorable  conditions  existing  in  the  last  effect  must  be  counter- 
balanced by  making  others  more  favorable  but  without  affecting 
the  efficiency  of  the  first  effect. 

The  means  at  hand  for  increasing  the  heat-transference  of  the 
last  effects  are  to  increase  the  temperature-fall  and  to  keep  the  boil- 
ing-temperature not  too  low  by  too  high  a  vacuum.  If  the  vacuum 
rises  much  above  60  cm.  (24  inches),  it  is  true  that  the  temperature- 
fall  increases  more  in  proportion  to  every  centimeter  rise  in  the 
vacuum,  but  the  heat-transference  coefficient  decreases  in  much 
greater  proportion  as  the  boiling- temperature  sinks.  Hence  it 
appears  useless  to  keep  the  vacuum  higher  than  60  cm.,  and  indeed 
such  high  vacuums  are  difficult  to  reach  unless  a  large  amount  of 
cold  water  and  a  perfectly  working  vacuum-pump  are  available. 
Taking  all  circumstances  of  actual  practice  into  consideration,  it  is 
best  to  work  at  a  vacuum  of  about  60  cm. 

Another  means  of  increasing  the  efficiency  of  the  last  effects  and 
likewise  of  the  whole  multiple  effect  is  to  increase  the  temperature- 
fall.  Since,  as  has  just  been  shown,  the  boiling-temperature  cannot 
be  advantageously  lowered  more  than  that  corresponding  to  60  cm. 
vacuum,  the  temperature  of  the  heating-vapors  must  be  raised. 
It  follows  that  these  later  effects  should  be  made  smaller,  especially 
as  the  total  temperature-drop  of  the  whole  system  is  fixed  once  for 
all.  The  apportioning  of  this  temperature-drop  must  be  such  as 
to  have  in  the  first  effect  the  smallest  practicable  difference  in 
temperature  between  the  steam  and  the  boiling  juice,  while  the 
remaining  temperature-drop  should  be  greater  proportionately  in 
each  succeeding  effect.  It  follows  further  that  the  first  effect  must 
have  the  greatest  heating-surface,  as  there  is  less  temperature-drop 
here  for  evaporating  the  necessary  amount  of  water  from  the  juice, 
while  the  last  effects  require  proportionately  less  heating-surface. 

Besides,  the  first  effects  should  be  made  still  larger,  so  as 
to  give  steam  for  the  heating  and  boiling  of  the  juice  and  sirup. 
It  will  depend  mainly  on  the  extent  and  the  heat-transference 
efficiency  of  the  heating-surfaces  in  the  cookers  and  heaters,  the 
initial  temperature  of  the  juice,  and  the  temperature  required  as  to 
whether  the  heating-vapors  be  taken  from  the  first  or  second  effect 


EVAPORATION.  151 

or  whether  one  shall  furnish  heat  for  boiling  and  the  other  for 
heating. 

If  the  boiling-point  in  the  first  effect  is  too  low  for  heating  an  i 
boiling,  because  the  later  effects  are  too  large  and  the  vapor 
pressure  in  all  the  effects  are  too  low,  the  pressure  can  be  raised 
in  the  first  effect  or  in  both  first  and  second  effects  as  high  as  is 
compatible  with  the  pressure  of  the  exit-vapors  by  inserting  throt- 
tle-valves in  the  vapor-pipes.  Such  arrangements  should  only  be 
installed  under  the  express  condition  that  they  are  recommended 
by  experts,  and  should  be  so  constructed  that  they  could  not  be 
completely  closed. 

Cold  raw  juice  especially  can  be  heated  by  the  exhaust-vapors 
of  the  last  effect,  because  these  have  a  temperature  of  60°-70°  (140°- 
158°  F.),  while  the  juice  is  at  only  25°-35°  (77°-95°  F.).  This 
method  of  heating  is  very  desirable  because  it  is  entirely  without 
fuel-cost,  since  the  heat  would  otherwise  be  lost.  Such  a  heater 
lias  no  influence  on  the  size  of  the  evaporator  nor  on  cost  of  manu- 
facture, because  it  is  placed  in  the  exit-pipe  to  the  dry  condenser. 

All  the  other  liquors  require  for  their  heating  steam  of  90°-100° 
(194°-212°  F.)  or  over.  This  must  consequently  be  taken  from 
the  first  two  effects  of  a  quadruple-effect  evaporator  or  from  the 
first  effect  of  a  triple,  or  from  the  juice-cooker,  if  there  is  one,  and 
first  effect. 

The  so-called  juice-cooker  or  preheater  is  an  additional  vertical 
evaporating-vessel  of  the  multiple  system  which  is  heated  with 
high-pressure  or  reduced  live  steam. 

The  installation  of  such  a  juice-cooker  is  especially  desirable 
where  exhaust-steam  is  not  available  for  the  evaporation  and  live 
steam  is  consequently  used,  and  also  where  steam  of  the  highest 
available  pressure  must  be  used  for  cooking  and  heating,  such  as 
cannot  be  had  from  the  quadruple  effect. 

In  the  juice-cooker  the  steam  for  boiling  may  be  as  high  as  J 
of  an  atmosphere  (11  Ibs.)  or  even  1  atmosphere  (15  Ibs.),  the 
boiling  temperature  being  raised  to  llo°-12()0  (239°-248°  F.)  without 
fear  of  decomposing  sucrose  or  that  the  juice  will  be  made  darker, 
provided  it  is  sufficiently  alkaline.  By  use  of  such  high  pres- 


152  BEET-SUGAR  MANUFACTURE. 

sures  the  heating-surfaces  of  cooking  and  heating  apparatus  can 
be  made  proportionately  small  and  the  steampipes  of  smaller 
diameter.  It  is  on  this  account  that  these  juice-cookers  have 
become  popular  in  spite  of  many  practical  objections  to  them. 
In  most  factories  they  use  one  juice-heater,  but  some  use  two  or 
even  three  the  first  heated  by  live  steam,  the  second  heated  from 
the  exhaust-steam  from  the  first.  This  arrangement  is  par- 
ticularly recommended  in  cases  where,  owing  to  the  centralization 
of  the  motive  power,  little  exhaust-steam  is  available.  The 
live  steam  is  thus  utilized  twice,  and  the  waste  vapors  can 
then  be  used  in  conjunction  with  the  evaporator  vapors  for 
heating  and  boiling. 

There  are  certain  difficulties  connected  with  the  working  of  the 
juice-heaters,  partly  on  account  of  their  being  outside  the  real 
evaporating  system,  which  can,  however,  be  overcome.  In  the 
first  place  it  is  not  advisable  to  draw  or  pump  all  of  the  juice 
through  the  juice-heater,  because  it  is  unnecessary  that  all  of  the 
juice  should  be  brought  to  such  high  temperature.  When  the 
juice  is  drawn  over  into  the  first  effect  of  the  multiple  evaporator 
from  the  juice-cooker  it  gives  off  its  excess  heat  in  the  form  of 
steam,  so  that  considerably  less  engine  exhaust-steam  will  be  con- 
densed and  proportionally  more  live  steam  will  be  used.  It  is 
advisable,  therefore,  to  draw  in  to  the  juice-cooker  only  enough 
juice  to  keep  its  density  not  higher  than  15°-20°  Brix.  (8.5°-11.3° 
Be.),  while  the  excess  .of  juice  is  drawn  directly  into  the  first  effect, 
where  it  mixes  with  that  from  the  juice-heater.  Where  several 
juice-heaters  are  used  this  is  not  done.  As  it  is  absolutely  nec- 
essary to  keep  the  juice  moving  through,  owing  to  the  high  tem- 
perature, all  the  juice  goes  through  the  first  heater  and  then 
through  the  others. 

Another  difficulty  encountered  in. running  the  juice-heater 
according  to  the  usual  method  is  due  to  the  fact  that  more  work 
is  required  of  it  at  one  time  than  at  another.  For  instance, 
when  a  vacuum-pan  is  just  started,  very  much  steam  must 
be  used  to  thicken  the  sirup,  although  during  graining  but 


KVAPORATIOX.  153 

little  is  required.  It  may  happen  at  times  that,  owing  to  a 
momentary  stoppage  in  the  juice-pipe,  all  the  exhaust  can- 
not be  used  in  the  first  effect,  while  the  juice-cooker  at  the  same 
moment  needs  a  large  amount  of  steam.  The  result  is  that 
a  large  quantity  of  steam  is  taken  from  the  boilers,  while  the 
exhaust  blows  off  over  the  roof.  To  avoid  this  trouble,  there 
should  be  an  exhaust-steam  line  connected  with  the  steam  line 
of  the  last  juice-cooker  the  valve  of  which  should  as  a  rule  be  kept 
open  during  the  working  of  the  heater. 

There  is  then  a  common  pipe  system  for  the  exhaust  and  the 
steam  used  in  the  cooker,  from  which  lead  all  the  connections  to  the 
heating  and  boiling  apparatus.  The  last  juice-cooker,  therefore, 
controls  the  pressure  of  the  exhaust,  and  the  regulation  of  the  steam 
used  in  heating  simply  depends  on  the  pressure  desired.  In  this  way 
the  steam  will  be  used  in  the  most  efficient  and  reliable  manner,  and 
the  work  will  be  remarkably  uniform.  It  will  never  happen  that  the 
juice  foams  in  the  cooker,  because  the  evolution  and  escape  of  steam 
will  be  much  more  regular,  so  that  sudden  upheavals  caused  by  rapid 
falling  of  the  pressure  and  consequent  foaming  will  never  occur. 

If  the  juice-cooker  is  thus  introduced  into  the  common  steam 
system,  the  contrivances  so  often  recommended  for  controlling 
the  inflow  of  live  steam  which  are  regulated  by  the  pressure  in  the 
boiling-chamber  will  be  not  only  unnecessary  but  rather  superfluous, 
as  violent  and  rapid  pressure-changes  will  not  take  place,  and  the 
man  in  charge  has  merely  to  look  at  the  steam-gauge. 

Whether  a  juice-cooker  is  used  or  not,  the  evaporating-plant 
must  be  designed  so  as  to  give  under  all  conditions  sirup  of  the 
required  density,  even  if  irregularities  do  occur  in  the  work.  Ir- 
regularities of  this  sort  for  which,  it  is  needless  to  say,  often  all 
sorts  of  ideas  about  evaporating  apparatus  are  responsible,  can 
never  be  prevented  in  actual  practice;  they  are  partly  dependent 
on  special  conditions  in  the  sugar-house,  as,  for  instance,  on  extreme 
variations  in  the  amount  of  exhaust-steam  used  in  making  masse- 
c-uite  from  sirup  in  the  vacuum-pan  work.  Another  thing,  the 
juice-supply  is  never  uniform;  at  times,  owing  to  stoppages  of  the 
beet-slicers  or  uneven  pressure,  the  diffusion-juice  comes  irregularly, 
at  other  times  the  rate  of  carbonate  tion  varies,  again  the  filter- 


154  BEET-SUGAR  MANUFACTURE. 

presses  run  unevenly;  in  short,  there  are  frequent  cases  when  the 
juice  is  in  excess,  and  which  the  tanks  could  not  take  care  of  if 
the  evaporating  capacity  were  figured  for  an  average  juice-supply. 

The  capacity  of  an  evapora ting-plant  should  be  calculated  not 
only  with  allowance  for  steam  taken  for  heating  and  boiling,  but 
for  evaporating  the  desired  amount  of  juice  when  only  a  part  of 
this  steam  is  withdrawn.  Besides,  there  should  be  an  excess 
calculated  over  the  necessary  heating-surface  for  the  average  juice- 
yield:  (1)  of  about  10%  allowed  in  all  effects  for  occasions  when 
work  is  forced,  and  (2)  for  loss  in  heat-transference  of  the  heating- 
surfaces  from  scale.  Since  this  scale  is  formed  in  appreciable 
quantities  only  in  the  last  effects,  the  increase  in  the  heating-surface 
should  be  put  there.  While  an  increase  in  heating-surface  of  all 
effects  of  the  evaporating  system  helps  take  care  of  a  greater  juice- 
supply,  withdrawing  more  of  the  exit- vapors  for  use  in  boiling  and 
heating  from  any  one  effect  obviously  influences  only  that  effect 
and  the  one  ahead  of  it,  if  there  be  such.  Usually  this  irregular 
withdrawal  of  steam  affects  only  the  first  effect  and  the  juice- 
cooker.  It  is  not,  however,  necessary  to  reckon  the  area  of  the 
heating-surface  necessary  for  the  maximum  possible  quantity  of 
steam,  it  being  sufficient,  if  a  possible  increase  in  the  temperature 
of  the  vapors  is  taken  into  consideration,  to  calculate  the  heating-- 
surface for  the  average  quantity  of  steam  to  be  withdrawn.  As 
the  efficiency  of  an  evaporator  within  narrow  limits  is  practically 
proportional  to  the  temperature-drop,  and  since  this  temperature- 
drop  never  exceeds  6°-8°  C.  (11°— 14°  F.),  an  increase  in  the  tempera- 
ture of  the  steam  used  in  evaporating  of  2°-3°  C.  (3.5°-5.5°  F.) 
(corresponding  to  an  increase  in  the  exhaust-steam  pressure  of  0.2 
atmosphere  or  3  Ibs.)  will  be  enough  to  raise  the  efficiency  of  an 
effect  from  25  to  33  per  cent.  This  increase  is  quite  sufficient  to 
provide  for  even  maximum  variations  in  the  use  of  steam  in  the 
boiling  and  heating  plants. 

A  multiple  effect  by  no  means  works  in  a  fixed  mechanical 
routine.  Any  slight  changes  which  are  continually  occurring  in 
the  conditions  of  evaporating  or  in  other  existing  circumstances 
affect  its  efficiency  to  a  very  great  extent. 


EVAPORATION.  15.5 

The  temperature-drop  in  the  different  effects  shows  most 
variation,  and  on  this  depends  the  heat-transmission  coefficient  and 
consequently  the  efficiency  of  the  evaporator.  All  calculations  of 
heating-surface  are  based  on  a  certain  theoretical  standard  of 
evaporation,  which  is  no  less  valuable  even  if  later  conditions  of 
actual  practice  alter  it.  The  great  efficiency  of  the  multiple  effect  is 
not  equal  to  what  can  be  calculated  theoretically,  because  all 
conditions  of  practice  cannot  be  predicted. 

Experience  has  taught  us  to  arrange  evaporators  in  a  line 
consisting  of  elements  exactly  alike,  a  convenient  number  of  which 
are  united  in  one  body.  Each  element  is  trunk-shaped  and  has 
its  own  heating- chamber  filled  with  vertical  tubes.  This  heating- 
chamber  is  connected  by  a  branch  with  the  general  steam  system, 
and  the  tail-pipes  lead  by  one  or  several  branches  from  each  special 
heating-chamber  to  the  trap  system.  The  juice-circulation  in  such 
evaporators  must  be  especially  good,  since  each  separate  heating 
system  (effect)  has  to  be  separated  from  the  others  by  suitable 
space.  In  this  way  apparatus  already  installed  can  be  easily 
enlarged  without  great  expense  and  structural  alterations,  if  such 
increase  becomes  necessary.  Likewise  changss  in  the  heating- 
surface  of  different  elements  of  the  evaporator  can  be  easily  made 
if  these  appear  advantageous. 

The  basis  for  the  calculation  of  amount  of  heatimg-surface  is 
the  heat-transference  coefficient.  For  the  ordinary  vertical  or 
horizontal  trunk-shaped  evaporators  the  following  figures  can  bo 
taken  as  averages  for  practical  use. 

The  coefficients  in  a  quadruple  effect  are:  in  I  (including  the 
juice-cooker)  40-50,  in  II  30-40,  in  III  20-30,  in  IV  10-15. 

In  a  triple  effect:  in  I  40-50,  in  II  30-40,  in  III  12-15. 

A  necessary  requirement  in  the  application  of  these  figures  is 
that  the  apparatus  is  properly  handled  and  put  together.  If  the 
proper  amount  of  steam  is  calculated,  for  juice-evaporation  and  for 
withdrawal  in  heating  and  boiling,  there  will  be  all  the  necessary 
data  for  figuring  out  the  heating-surfaces.  (See  Appendix  II.) 
It  is  especially  important  to  figure  the  temperature  of  the  exit- 
vapors  low  enough  and  make  the  temperature-drop  in  the  first 


156  BEET-SITGAR   MANUFACTURE. 

effect  small.  The  heating-surface  of  this  effect  should  be  especially 
large,  for  this  extensive  heating-surface  is  of  the  greatest  value,  as 
it  insures  the  efficiency  of  the  whole  multiple  effect  under  all 
possible  conditions. 

The  value  of  an  evaporating-plant  whose  capacity  has  been 
calculated  in  the  manner  described  depends  on  how  the  stearn  of 
the  factory  is  used  for  heating  purposes.  Theory  and  practice  have 
shown  that  the  economy  is  greater  the  more  the  steam  is  taken 
from  the  vapors  of  the  evaporators  for  boiling  and  heating  and  the 
use  of  live  steam  avoided  as  much  as  possible.  Hence  a  better 
utilization  can  be  made  of  the  vapors  of  a  quadruple  effect  for 
heating  and  boiling  than  of  those  of  a  quintuple  or  sextuple  effect, 
where  such  use  is  not  advantageous.  A  triple  effect  can  do  even 
better,  provided  fuel  is  not  too  expensive.  The  juice  extraction 
does  not  have  such  a  great  influence  on  the  work  of  sugar-houses 
with  well-designed  evaporators  as  it  used  to  in  more  primitive  plants. 
As  shown  in  the  calculation  of  Appendix  II,  the  total  steam  con- 
sumption of  a  factory  per  100  kg.  (220  Ibs.)  of  beets,  when  the 
extraction  was  115  kg.  (223  Ibs.)  of  diffusion  juice  was  61.7  kg. 
(135.7  Ibs.)  being  only  3  kg.  (6.6  Ibs.)  less,  or  58.7  kg.  (12.91  Ibs.), 
when  the  extraction  was  105  kg.  (231  Ibs.).  The  entire  amount  of 
steam  used  in  the  factory  for  evaporating,  when  the  evaporators 
are  properly  calculated  and  of  convenient  simplicity  for  best 
practical  work,  is,  exclusive  of  cooling-losses,  about  60  per  cent  of 
the  weight  of  the  beets.  No  house  ought  to  use  more  than  70  per 
cent,  of  steam,  and  all  of  this  steam  should  be  used  as  exhaust  or 
live  steam  in  the  juice-cooker  and  the  first  effect,  provided  no  live 
steam  is  necessary  for  the  overflow-heaters  of  the  diffusion  plant 
as  when  they  are  heated  by  direct  injection.  As  shown  by  tables 
in  Appendix  III,  if  the  number  of  effects  of  an  evaporating-plant 
is  increased,  which  of  course  means  better  utilization  of  the  exhaust- 
steam,  or  improvements  are  made  in  the  application  of  the  heat 
of  the  exit-vapors  in  boiling  and  heating,  obviously  the  steam- 
consumption  can  be  still  further  cut  down.  The  more  the  steam 
is  economized  in  evaporation  the  more  evident  become  the  losses 
by  cooling  and  other  wastes,  and  arc  forced  on  our  attention. 


EVAPORATION.  157 

In  every  case  where  improvements  are  made,  careful  calcula- 
tions will  show  whether  the  greater  coal-economy  resulting  has 
paid  for  the  increased  cost  of  installation  and  alterations. 

A  theoretically  interesting  method  of  multiple  steam-utiliza- 
tion, not  yet  introduced  into  actual  practice,  which  is  capable  of 
reducing  the  steam-consumption  still  more,  consists  in  compress- 
ing the  exit-vapors  of  the  first  and  second  effects  with  a  pump  to 
the  original  exhaust-steam  pressure  and  hence  restoring  its 
efficiency.  Evidently  such  procedure  is  only  practicable  where 
pumps  can  be  driven  by  water-power.  Moreover,  the  trouble 
would  be  that  the  compressed  vapors  would  be  strongly  super- 
heated. Highly  superheated  steam  is,  however,  entirely  useless 
for  evaporating  apparatus  because,  unless  it  is  cooled  to  th/» 
saturation-temperature,  it  acts  like  a  gas  and  gives  up  its  heat 
very  slowly  to  the  heating-surfaces.  Even  water-injection  does 
not  increase  the  heat-transference  sufficiently.  Again,  the  com- 
pressor-pump must  be  well  oiled,  and  in  consequence  the  com- 
pressed steam  contains  oil  which  sticks  on  the  heating-surfaces 
and  lessens  the  heat-transference.  This  trouble  can  be  overcome 
by  use  of  high-pressure  blowers  instead  of  ptimps. 

The  advantages  of  this  system  can  be  attained  without  the 
attendant  drawbacks  mentioned  if  steam-injection  apparatus  is 
used.  By  use  of  this  apparatus  exhaust-steam  of  low  pressure  can 
be  raised  by  live  steam  to  a  pressure  about  ?>  an  atmosphere  (8  Ibs.) 
higher  without  the  mixed  steam  losing  heat  or  undergoing  per- 
ceptible superheating. 

The  amount  of  exhaust-steam  which  can  be  brought  to  a  higher 
pressure  by  this  means  depends  on  the  boiler-pressure  and  the 
pressure-increase  desired.  To  compress  1  kg.  of  exhaust-steam 
about  J  an  atmosphere  (8  Ibs.)  2  kg.  of  live  steam  at  6  atmospheres 
(90  Ibs.)  pressure  are  necessary.  To  the  extent  that  live  steam  at 
high  pressure  must  be  used  in  the  evaporating-plant,  this  steam- 
jet  apparatus  can  be  recommended  as  a  very  inexpensive  con- 
trivance for  better  economizing  steam.  It  is  important  that  the 
jet  apparatus  always  works  with  full  boiler-pressure.  Since  the 
amount  of  live  steam  necessary  is  very  variable,  it  is  a  necessary 


158  BEET-SUGAR   MANUFACTURE. 

requirement  to  install  not  one  jet  apparatus  only,  that  works  at 
its  highest  efficiency  at  the  maximum  boiler-pressure,  but  several 
smaller  ones  which  collectively  have  the  same  capacity,  so  that  as 
many  can  be  put  into  action  as  the  amount  of  live  steam  available 
permits. 

The  steam-economy  which  can  be  attained  by  steam-jet  appara- 
tus on  the  first  effect  sucking  vapors  from  the  second  is  theoretically 
as  much,  approximately,  as  obtained  by  installing  a  juice- 
cooker. 

At  the  beginning  of  work  when  the  evaporating  apparatus  is 
not  running,  and  during  Sunday  stops  or  interruptions  of  the 
factory,  it  is  necessary  to  use  live  steam.  The  valves  in  evaporators, 
heaters,  and  pans  should  be  always  carefully  watched  to  prevent 
them  being  opened  through  carelessness:  they  should  be  locked 
or  the  wheels  taken  off.  The  best  way  is  to  have  a  large  stop-valve 
on  the  main  exhaust-line  leading  to  the  heaters  and  vacuum  appa- 
ratus and  through  which  the  necessary  live  steam  is  admitted. 
One  valve  can  be  looked  after  much  better  than  several. 

As  already  stated,  the  greatest  sugar-loss  from  decomposi- 
tion of  sucrose  does  not  occur  in  evaporators,  provided  the  highest 
boiling  temperature  does  not  exceed  115°-120°  C.  (239°-248°  F.) 
and  provided  the  juice  is  sufficiently  alkaline;  yet  it  cannot  be 
denied  that  a  small  amount  of  sucrose,  not  exceeding  a  few 
hundredths  of  a  per  cent.,  is  destroyed.  This  loss  increases  not 
only  with  the  temperature,  but  with  the  length  of  time  that  the  juice 
is  exposed  to  such  temperature.  For  instance,  of  100  parts  of 
sucrose  in  the  juice  at  100°  (212°  F.)  0.114  part  of  sugar  is 
destroyed  in  an  hour;  at  110°  (230°  F.)  0.163  part;  and  at  115° 
(239°  F.)  0.175  part.  The  average  time  that  juice  is  in  an 
evaporator  is  only  half  an  hour  if  the  temperature  is  115°  (239°  F.). 
In  apparatus  evaporating  at  an  average  temperature  of  100°  (212° 
F.)  and  consequently  slower,  the  juice  is  in  an  hour  and  the 
sugar-decomposition  is  consequently  greater. 

The  juice  is  likewise  delayed  in  the  evaporator  if  its  juice-content 
is  too  great  or  if  it  is  evaporated  with  too  little  temperature  drop. 
This  juice  content  is  too  great  if  the  juice-level  is  too  h'gh  during 


KVAPORATIOX.  159 

evaporating  or  if,  in  horizontal  evaporators,  there  is  too  much 
useless  space  below  the  tubes  in  vertical  apparatus  or  between 
tubes  in  the  horizontal  typ?.  Evaporating  should  be  done  under 
a  Imc  juice-head  and  the  apparatus  made  as  large  as  consideration 
of  juice-circulation  demands.  The  bad  habit  must  be  avoided  of 
filling  up  the  evaporator  with  juice  when  there  i.s  a  large  supply 
of  thin  liquor  on  hand  or  the  sirup  is  coming  off  too  heavy,  and 
thereby  at  once  lowering  the  efficiency  of  apparatus  of  even  the 
largest  capacity.  There  will  be  too  much  juice  in  the  evaporator 
also,  aside  from  troubles  in  the  factory,  if  the  heating-surface  is 
too  great  for  the  amount  of  thin  liquor. 

The  boiling-point  of  no  evaporator  should  rise  above  120° 
(248°  F.),  at  least  not  for  any  length  of  time,  as  the  sucrose  decom- 
position increases  very  fast  with  every  degree  rise  above  this  tem- 
perature. In  an  hour,  100  parts  of  sugar  lose  by  decomposition 
0.28  parts  at  120°  (248°  F.)  0.53  parts  at  125°  (257°  F.)  and  2.05 
parts  at  130°  (266°  F.). 

If,  for  any  reason,  thin  liquors  must  be  evaporated  which  are 
neutral  or  weakly  acid  (a  manner  of  working  which,  taking  every- 
thing into  consideration,  scorns  utterly  wrong),  the  boiling-point 
ought  never  to  rise  above  100°  (212°  F.),  and  even  this  is  risky. 
Under  such  circumstances  evaporating  cannot  be  done  with 
economy.  Considerable  sugar-loss,  accompanied  with  a  large 
drop  in  alkalinity,  occasionally  occurs  from  the  introduction  of 
juice  infected  with  bacteria  coming  from  badly  designed  juice 
catchers  (see  above).  Likewise  evaporators  which  are  so  con- 
structed as  to  have  a  space  under  the  tubes  where  the  juice  can 
cool  will  breed  active  colonies  of  bacteria,  especially  leuconostoc. 
Xo  such  losses  will. occur  if  proper  construction  is  used  for  pre- 
venting entrainment.  If  there  are  juice  catchers,  it  is  advisable 
to  send  any  juice  they  trap  back  to  the  defecation  instead  of 
letting  it  go  into  the  thickened  juice. 

Control  of  evaporating  apparatus  has  these  objects:  (1)  Regula- 
tion of  the  steam-supply  according  to  the  thin  liquor  on  hand;  (2) 
Preventing  the  steam-pressure  in  the  first  effect  and  the  juice- 
heater  from  rising  above  the  upper  limits  prescribed;  (3)  Keeping 


160  BEET-SUGAR  MANUFACTURE. 

the  vacuum  in  the  last  effect  uniformly  at  the  proper  point;  (4) 
Seeing  that  the  juice  is  at  the  lowest  possible  level  in  all  effects; 
(5)  Taking  care  that  the  sirup  is  discharged  at  a  uniform  rate  and 
density.  If  these  details  are  rigorously  seen  to,  all  others  will 
take  care  of  themselves. 

Since  the  engine-exhaust  is  usually  inadequate  for  the  evapora- 
tors, it  is  seldom  necessary  to  regulate  the  exhaust-valve.  When 
there  is  lack  of  juice,  however,  this  valve  must  be  closed  and  the 
steam  allowed  to  blow  off  through  an  escape-valve.  It  is  never 
advisable  in  such  cases  to  take  in  water  instead  of  juice  and  evapo- 
rate it  so  as  to  stop  the  steam  blowing  off,  since  this  always  dam- 
ages the  juice. 

The  pressure  in  the  steam-chamber  of  the  first  effect  ought 
never  to  be  higher  than  what  is  best  for  the  engines,  since  excessive 
back-pressure  of  the  exhaust  impedes  them  and  lowers  their 
economy.  The  introduction  of  live  steam  or  of  the  exhaust  from 
the  juice-cooker  into  the  main  exhaust  system  must  consequently 
be  regulated  by  the  pressure  in  the  steam-chamber  of  the  first 
effect. 

The  vacuum  in  the  last  effect  must  be  kept  uniform,  since  any 
drop  makes  a  corresponding  increase  in  pressure  in  the  preceding 
effects.  Especially  important  is  keeping  the  concentration  of  sirup 
uniform,  since  any  increase  in  the  density  of  the  sirup,  especially 
above  60°  Brix  (33°  Be.),  makes  a  marked  increase  in  the  boiling- 
point  and  viscosity  and  consequent  perceptible  increase  in  the  pres- 
sure of  the  preceding  effects. 

Raising  the  boiling-point  diminishes  the  true  temperature-fall, 
while  increase  in  viscosity  lowers  the  heat-transference  coefficient, 
which  for  sirup  of  60°  Brix  (33°  Be.)  is  only  about  f  that  of  water, 
sinking  to  about  J  for  sirup  of  70°  Brix  (38°  Fe.).  The  statement 
that  the  smaller  specific  heat  of  the  sirup  has  influence  on  this 
coefficient  is  erroneous.  A  uniform  concentration  of  sirup  is  also 
most  advantageous  for  working  it  up  in  the  processes  which  follow. 
Hence  frequent  spindle-readings  should  be  made,  or,  what  is  better, 
use  automatic  apparatus  for  showing  the  density  constantly.  A 
specially  constructed  hydrometer  cylinder  with  overflow-pipe 


EVAPORATION.  161 

attached  to  the  discharge-pipe  of  the  sirup-pump  is  simple  and 
convenient,  as  a  spindle  can  be  kept  floating  in  the  sirup. 

Montejus  are  seldom  used  for  taking  away  sirup.  Pumps  are 
much  more  convenient  in  every  way,  particularly  because  the  sirup 
can  be  drawn  off  continuously  and  its  density  kept  uniform  much 
more  easily.  These  pumps  overcome  the  vacuum  of  the  apparatus 
better  if  they  are  set  as  low  as  possible,  so  that  the  juice-head  in 
part  balances  the  effect  of  the  vacuum. 

The  flow  of  juice  from  one  effect  to  another  should  be  continuous 
and  not  in  gushes.  Skillful  workmen  soon  learn  to  set  the  valves 
so  that  they  seldom  have  to  be  altered,-  especially  when  the  juice 
is  coming  to  the  evaporator  regularly.  The  liquor-entrance  pipes 
should  never  discharge  over  the  heating-tubes,  but  always  in  the 
bottom  and  through  a  perforated  pipe  which  lies  under  the  tubes. 
Since  the  juice  goes  from  an  effect  under  higher  pressure  into  one 
at  lower  pressure,  it  is  superheated  as  it  enters  the  latter  and 
immediately  gives  off  a  large  amount  of  steam  which  atomizes  the 
juice  and,  when  the  opening  of  the  pipe  is  above  the  tubes,  causes 
a  loss  by  entrainment.  If  the  juice  enters  under  the  tubes,  these 
steam-bubbles  which  are  formed  are  very  useful  in  improving  its 
circulation. 

The  juice-gauge  must  be  properly  set  if  it  is  to  indicate  properly; 
that  is,  the  lower  end  must  be  connected  below  the  tubes  and  the 
upper  end  above  them.  Juice-gauges  which  are  entirely  above  the 
tubes  are  of  no  use.  Large  sight-glasses  and  also  illuminating-glasses, 
for  easily  seeing  the  interior,  should  be  placed  in  all  apparatus. 

If  all  these  directions  are  followed,  every  apparatus  will  show 
certain  characteristics  which  can  be  considered  normal  and  constant 
for  every  effect,  providing  the  steam-pressures  and  the  vacuum  on 
the  condensers  remain  constant,  and  which  change  in  a  perfectly 
regular  way  if  either  the  steam  or  the  vacuum  changes. 

Variations  from  these  regular  values  are  due  to  interruptions  in 
the  running  of  the  apparatus  and  are  always  followed  by  diminish<><  1 
efficiency.  If  these  irregularities  appear  about  the  end  of  the  week 
or  when  the  vacuum  in  the  last  effect  remains  constant,  but  the 
pressure  of  the  preceding  effects  goes  up,  it  is  a  sign  of  scale-deposit 


162  BEET-SUGAR   MANUFACTURE. 

on  the  tubes.  Directions  as  to  duration  of  boiling  out  and  the 
liquors  to  use  for  removing  scale  have  already  been  given. 

Irregularities  in  the  pressure  relations  of  the  effects  also  come 
from  incomplete  removal  of  condensation-waters  ("  sweet-waters") 
from  the  steam-chambers,  the  area  of  the  heating-surface  being 
diminished.  In  order  to  detect  presence  of  water  in  the  heating- 
chambers,  they  should  be  provided  with  guage-glasses. 

The  removal  of  condensed  water  from  heating-chambers  where 
the  steam  is  at  more  than  atmospheric  pressure  is  made  by  float- 
traps,  which  should  be  inspected  frequently  to  make  certain  that 
they  remove  the  water  completely  but  allow  no  steam  to  pass. 
The  water  condensed  in  the  last  effect  is  either  pumped  away  or 
carried  by  a  pipe  into  a  tank  placed  low,  so  that  its  water-level  is 
below  that  corresponding  to  the  highest  vacuum  in  the  heating- 
chamber,  say  6-7  meters  (19-22  ft.)  below  it.  Sometimes  con- 
densed water  from  the  other  effects  is  led  into  this  tank  or  well, 
being  pumped  thence  to  where  it  is  needed,  but  this  mixture  of  hot 
and  cooler  water  is  not  advisable;  it  is  better  to  keep  that  which 
is  over  100°  (212°  F.)  separate  and  use  it  for  boiler-feed,  employing 
the  cooler  for  diffusion,  sweetening  off  filter-presses,  slaking  lime,  etc. 

In  some  factories  attempts  have  been  made  to  utilize  the  heat 
of  this  hot  condensed  water  for  evaporation  by  passing  it  over 
from  one  heating-chamber  into  the  next  following,  so  that  the 
water  under  the  diminished  pressure  of  this  second  chamber  gives 
off  its  superheat  in  the  form  of  steam.  Finally  all  of  the  water 
comes  to  the  heating-chamber  of  the  last  effect  and  is  discharged 
at  the  temperature  of  this  chamber.  If  this  method  is  used,  care 
must  be  taken  to  have  the  tail-pipes  specially  large  in  order  to 
prevent  waterlogging.  Any  special  advantage  in  this  is  not  clear, 
as  this  heat,  although  utilized  in  the  evaporator,  is  lost  by  the 
boilers. 

The  pressure-relations  will  also  change  if  the  juice  foams  badly, 
whatever  the  cause.  Foaming  within  certain  limits  is  very  advan- 
tageous for  evaporation  at  a  low  juice-level,  as  has  already  been 
explained.  If,  however,  the  foaming  is  too  strong,  the  heating-sur- 
faces are  no  longer  sufficiently  wetted.  Every  dry  spot  is  useless, 


KVAPOilATlOX.  Hi.'* 

and  consequently  bad  foaming  always  raises  the  pressure  in  the 
heating-chamber.  A  fat  whose  viscosity  is  as  small  as  possible 
has  to  be  used  to  stop  this  foaming,  and  as  little  as  practicable, 
since  lime  soaps  and  undecom posed  fats  make  trouble  both  in  the 
evaporation  and  in  the  sirup-filtration.  The  fat  can  be  introduced 
through  the  butter-cup  in  effects  boiling  below  atmospheric  pressure; 
in  those  boiling  higher  an  oil-pump  must  be  used. 

A  low  vacuum  in  the  last  effect  and  consequent  high  pressures 
in  the  preceding  effects,  a  trouble  which  is  frequently  experienced 
at  the  beginning  of  the  campaign,  is  caused  by  leaks  in  the  joints 
of  the  apparatus  and  vapor-pipes  lowering  the  vacuum  on  account  of 
the  air  entering  the  condenser  and  overloading  the  air-pump. 
Those  leaks  which  cannot  be  detected  by  the  noise  of  the  air  rushing 
in  can  be  found  by  running  over  the  joints  with  a  lamp-flame,  and 
must  be  stopped  up  with  cement. 

No  good  reason  has  been  found  for  making  a  change  in  the 
simple  methods  of  running  evaporating  apparatus.  Proposals  for 
altering  them  have  never  been  popular  in  actual  practice,  and  it  is 
useless  to  detail  propositions  which  are  frequently  made  on  paper 
but  have  never  been  worked  out  by  actual  experience. 


CHAPTER  XIII. 
THE  CONDENSATION  OF  THE  EVAPORATION-VAPORS. 

WHEREAS  in  the  double-effect  evaporator  that  was  used  years 
ago  there  was  a  large  amount  of  juice-vapors  to  be  condensed, 
owing  to  the  slight  utilization  of  these  vapors  for  heating  and 
evaporation,  to-day,  with  the  more  economical  arrangement  of 
the  evaporation-vessels,  there  is  but  a  relatively  small  amount  of 
vapor  which  reaches  the  condensers. 

Everywhere  that  there  is  a  heating  or  boiling  apparatus  there 
is  a  corresponding  condensation  of  steam.  Consequently  all  of  the 
heating  and  boiling  apparatus  may  be  regarded  as  condensers,  and 
indeed  as  surface  condensers.  However,  when  the  term  condenser 
is  ordinarily  used  in  connection  with  the  sugar  industry,  reference 
is  made  to  the  injection-condensers,  whose  sole  purpose  is  to  con- 
dense steam  or  vapor. 

In  the  case  of  an  extensive  heating  of  the  juice  and  its  evapora- 
tion in  a  quadruple  effect,  there  will  be  from  100  kilograms  of 
water,  corresponding  to  about  100  kilograms  of  beets,  only  about 
10  kilograms  of  vapor  given  off  by  the  last  effect  to  pass  over  into 
the  condenser;  although  even  a  part  of  this  vapor  may  be  utilized 
for  heating  the  raw  juice  and  condensed  in  the  preheaters.  The 
remaining  90  kilograms  of  water  are  condensed  upon  the  heating- 
surfaces  of  the  evaporating,  heating  and  boiling  apparatus,  and 
recovered  in  the  form  of  pure  condenser-water  containing  a  little 
ammonia. 

Besides  the  vapors  from  the  last- juice  effect  of  the  evaporator, 
those  from  the  boiling  apparatus  must  also  be  condensed.  Ac- 
cording to  the  density  of  the  sirup  there  will  be  between  10  and 

164 


THE  CONDENSATION  OF  THE  EVAPORATION- VAPORS.      165 

15  kilograms  of  water  evaporated  from  each  100  kilograms  of 
beets,  or  in  other  words  there  will  be  at  least  as  much  vapor  to 
condense  coming  from  the  vacuum-pans  as  from  the  last  effect  of 
the  multiple  evaporator,  but  with  the  difference  that  there  will 
be  a  practically  uniform  evolution  of  vapor  from  the  latter  during 
the  whole  of  the  twenty-four  hours  in  a  day,  whereas  the  amount  of 
vapor  from  the  vacuum-pans  varies  from  time  to  time  very 
considerably.  Hence  the  condensing  apparatus  for  the  latter 
should  be  figured  not  for  the  average  amount  of  vapor 
given  off,  but  from  the  maximum  amount  evolved  at  any 
time. 

Every  condensation  plant  consists  of  an  injection-condenser 
and  an  air-pump. 

The  air-pumps  are  either  wet  or  dry — they  either  pump  only  the 
uncondensed  gases  from  out  of  the  condenser,  or  they  pump  out 
as  well  the  hot  water  which  has  effected  the  condensation.  The 
wet  air-pumps  possess  the  disadvantage  that  scale  is  almost  always 
deposited  in  them  from  the  hot  water,  and  furthermore,  when 
they  are  used,  the  advantage  gained  from  using  a  counter-current 
condenser  is  to  some  extent  neutralized,  because  the  cooled  gases, 
as  they  come  in  contact  with  the  hot  water,  are  warmed  again, 
occupy  a  greater  volume  and  consequently  diminish  the  efficiency 
of  the  pumps.  Therefore  dry  air-pumps  are  to  be  preferred  in  the 
sugar-factory,  preferably  with  high  vertical  condensers  from  which 
the  water  (hot-well  water,  as  it  is  called)  flows  off  through  a  leg- 
pipe  or  barometrical  tube. 

Counter-current  condensers  are  most  used,  and  in  these  the 
vapors  enter  at  the  bottom;  as  they  pass  upward  they  come  in  con- 
tact with  a  current  of  water  flowing  in  the  opposite  direction.  The 
disadvantage  that  was  formerly  found  in  these  condensers,  which 
prevented  their  adoption  and  gave  rise  to  preference  for  the  less 
efficient  parallel  condensers,  was  that  the  air-pumps  were  drowned  by 
their  damming  up,  resulting  in  irregular  working  of  the  system. 
This  evil  has  been  overcome  by  making  the  condensers  very  tall 
and  of  large  diameter,  and  by  adding  spray-plates,  sufficiently  apart 


166  BEET-SUGAR   MANUFACTURE. 

from  one  another,  particularly  at  the  lower  portions  of  the  con- 
denser where  the  vapors  enter.  It  has  been  found  advantageous  not 
to  introduce  the  vapors  at  the  very  bottom  of  the  condenser,  but 
high  enough  above  the  bottom  so  that  there  is  space  left  for  the 
vapors  to  move  downward  for  a  little  way  with  the  current 
of  descending  water.  In  this  way  all  damming  up  of  the  con- 
densers, which  is  otherwise  sometimes  met  with  even  in  condensers 
of  normal  size,  is  prevented.  The  inner  arrangement  of  the  con- 
denser may  be  quite  different  in  the  various  types.  In  one  form 
the  water  flows  along  a  winding  path,  in  another  it  falls  cataract 
fashion  over  plates  set  diagonally  against  one  another,  while  in 
still  another  type  the  water  falls  like  rain  in  fine  drops.  For 
sugar-factory  purposes  all  of  these  different  forms  work  satis- 
factorily, if  by  the  injection  of  a  sufficient  amount  of  cold  water 
the  desirable  vacuum  of  about  60  centimeters  can  be  readily 
produced,  and,  as  has  been  shown  in  the  preceding  chapter,  it  is  of 
no  particular  advantage  to  use  a  pump  constructed  for  a  higher 
vacuum.  For  the  vacuum-pans  also,  it  is  neither  necessary  nor 
desirable  to  have  a  greater  vacuum  than  60  cm. 

A  condenser  is  acting  satisfactorily  when  it  produces  a  vacuum 
of  about  60  centimeters  and  the  hot-well  water  flows  away  with 
a  temperature  not  more  than  10  degrees  lower  than  that  of  the 
vapors  coming  from  the  multiple  effect,  and  when  the  gases  passing 
into  the  pump  have  been  cooled  to  a  temperature  which  is  approxi- 
mately that  of  the  water  entering  the  condenser.  In  order  to  be 
able  to  control  the  work  of  the  condensers,  it  is  advisable  to  put 
thermometers  both  in  the  leg-pipe  and  in  the  suction-pipe  of  the 
air-pump.  When  these  thermometers  show  abnormal  temperatures 
immediate  information  is  given  of  poor  working  of  the  condensers, 
and  particularly  as  to  whether  too  much  or  too  little  water  is 
injected  into  the  condenser,  or  whether  the  pump  is  working 
properly. 

The  length  of  the  leg-pipe  should  be  at  least  10  meters  (33  ft.) 
from  the  lower  edge  of  the  condenser  to  the  upper  level  of  the 
hot-well.  Even  if  this  height  is  not  absolutely  essential  with 


THi:   mNDKNSATIOX   OF  THE  EVAPORATIOX-VAPORS.     107 

ordinary  vacuum  corresponding  to  60  cm.  of  mercury  column,  it 
is  always  advisable  to  make  it  as  much  as  this  because  it  is  im- 
possible entirely  to  avoid  deviations  in  the  height  of  the  water- 
column  in  the  leg-pipe,  and  these  deviations  sometimes  amount  to 
as  much  as  one  meter  (3  ft.)  or  more.  The  leg-pipe  should,  further- 
more, be  of  large  diameter,  especially  when  the  water  contains 
considerable  sand  and  small  stones,  which- would  clog  up  the  pipe 
during  the  campaign  if  it  were  too  narrow.  During  the  campaign 
it  is  impossible  to  clean  this  pipe  without  stopping  all  of  the  work, 
as  it  is  very  important  that  the  condenser  should  be  in  constant 
working  order. 

The  amount  of  injection-water  required  depends  altogether 
upon  the  temperature  of  the  hot-well  as  compared  with  that 
of  the  hot  vapors  and  of  the  injection-water.  Under  ordinary 
conditions  when  the  difference  between  the  temperatures  of  the 
vapors  which  are  at  62°  to  65°  C.  (144°-149°  F.)  and  the  hot-well 
is  about  10°  C.,  and  the  injection-water  is  from  10°  to  15°  C.  (50°- 
60°  F.),  it  will  be  necessary  to  inject  about  15  kilograms  of  water 
for  one  kilogram  of  vapor;  or  reckoned  another  way,  it  will  require 
about  150  kilos  of  water  for  the  vapors  from  the  first  concentration 
of  the  juice,  and  from  150  to  225  kilos  for  the  vapors  from  the  final 
boiling  dowrn  of  the  juice,  for  every  100  kilos  of  beets.  If  the 
vacuum  be  increased,  the  difference  in  temperature  between  the 
vapors  and  the  injected  wrater  is  lessened  and  consequently  more 
of  the  latter  must  be  used. 

The  amount  of  injected  water  used  corresponds  to  the  calculated 
amount  only  when  the  vapors  come  off  regularly,  as  is  the  case  with 
vapors  from  the  first  concentration  of  the  juice  but  not  with  the 
vapors  from  the  vacuum-pans.  The  amount  of  water  required  is 
particularly  variable  when  each  boiling  apparatus  is  provided  with 
its  own  special  condenser  and  a  special  air-pump;  its  control  is 
much  more  difficult,  and  the  plant  is  expensive. 

It  is,  therefore,  generally  customary  to  make  use  either 
of  one  common  condenser  or  at  least  a  central  air-pump. 
It  is  unquestionably  true,  with  regard  to  the  amount  of 


168  BEET-SUGAR   MANUFACTURE. 

water  consumed  and  the  simplicity  of  the  working,  that  the 
centralizing  of  the  condenser-plant  is  the  most  satisfactory. 
On  the  other  hand,  it  is  claimed  that  the  large  vapor-valves 
which  must  be  inserted  in  the  pipes  before  each  single 
apparatus,  in  order  to  be  .  able  to  cut  out  any  one  of  them 
from  the  system,  are  hard  to  keep  tight,  and  further  that  the 
boiling  down  of  the  sirup  to  make  it  crystallize  is  more  difficult  where 
the  vacuum  is  kept  uniform  than  when  the  pan  man  can  regulate  the 
vacuum  at  will  by  turning  the  water  on  or  off  at  each  separate 
condenser.  This  last  objection  is,  however,  a  weak  one,  because  it 
is  only  a  matter  of  practice  for  the  pan  man  to  be  able  to  conduct 
the  boiling  down  equally  good  at  a  constant  vacuum.  In  fact  it  is 
really  simpler  to  boil  at  uniform  vacuum.  When  it  is  desired  to 
boil  a  particularly  uniform  product;  say  coarse  granulated  sugar, 
it  is  perhaps  easier  for  most  sugar-boilers  to  make  the  necessary 
changes  in  the  vacuum  with  the  separate  condensers  than  by 
regulating  the  vapor-valve.  These  latter  valves  are  manufactured 
so  well  at  the  present  time,  and  they  are  made  so  tight  by  means 
of  vulcanized  fibre,  that  the  other  reasons  against  the  use  of  a 
centralized  condenser  system  are  no  longer  tenable.  Gate-valves 
have  also  proved  satisfactory.  As  a  rule,  the  vapor-pipes,  and  in 
consequence  the  valves,  of  vacuum-pans  are  made  too  large. 
This  not  only  increases  the  expense,  but  also  the  difficulty  in  keep- 
ing the  valves  tight. 

When  a  central  pump  works  different  condensers  it  is  necessary 
to  insert  a  valve  in  the  suction-pipe  of  each  separate  condenser, 
for  cutting  it  out.  This  arrangement  is  very  convenient  in  many 
ways,  although  considerably  more  water  will  be  required  than  is 
the  case  with  a  single  condenser,  because  there  is  no  equalization 
in  the  rates  at  which  the  vapors  come  from  the  different  concen- 
trators as  when  a  single  condenser  is  used.  It  is  necessary  to  give 
more  attention  to  separate  condensers,  particularly  if  economy  in 
the  use  of  the  water  is  desired. 

"  In  factories  where  there  is  no  scarcity  of  fresh  water  the  hot- 
well  water  serves  partly  as  pressure-water  in  the  diffusers,  but  is 


THE  COXDEXSATTOX  OF  THE  EVAPORATING  VAPORS.  169 

chiefly  used  for  washing  beets  and  in  the  hydraulic  carrier. 
Where  there  is  scarcity  of  water,  the  hot  well-water  is  cooled  by 
running  it  over  steps  or  into  cooling  and  spraying  appliances,  so 
that  it  reaches  a  temperature,  dependent  partly  upon  the  out- 
door temperature  and  the  amount  of  wind,  low  enough  so  that  it 
can  be  used  over  again  in  the  factory  and  also  for  condensing 
purposes. 


CHAPTER  XIV. 

CARBONATATION  AND  FILTRATION  OF  THE  CONCENTRATED 
JUICE  OR  SIRUP. 

SIRUP  from  the  evaporators  has  a  }Tellow  or  brown  color,  and  is 
turbid  from  a  fine  precipitate  which  separates  out  during  evapora- 
tion. Its  alkalinity,  as  has  already  been  stated,  depends  on  the 
alkalinity  of  the  thin  liquors  and  the  composition  of  the  juice. 
The  decrease  in  alkalinity  during  evaporation  will  be  in  proportion 
to  the  amount  of  ammonia,  amido  or  albuminous  substances,  invert, 
sugar,  and  lime  salts  held  in  the  thin  liquor.  If  such  decrease  did 
not  take  place,  a  sirup  of  60°  Brix  (33°  Be.)  should  have  five  times 
the  alkalinity  of  a  thin  liquor  of  12°  Brix  (6.8°  Be.),  while  as  a  rule 
the  alkalinity  of  sirup  is  only  from  three  to  four  times  greater,  so  that 
the  balance  either  is  distilled  as  ammonia  or  neutralized  by  the 
alkalies  combining  in  reactions  with  the  decomposition-products 
of  the  nitrogenous  substances,  invert-sugar,  and  lime  salts. 

Moreover,  the  color  of  sirup  is  darker  than  corresponds  ta  the 
concentration.  If  sirup  is  diluted  with  water  to  the  original 
concentration  of  the  thin  liquor,  it  will  be  darker  than  thin  liquor. 

The  normal  alkalinity  of  the  uncarbonatated  sirup  is  from 
0.07  to  0.15  per  cent.  Since  a  sirup  as  strongly  alkaline  as  this 
is  not  suitable  to  work  up  in  the  vacuum-pan,  it  is  carbona- 
tated  either  with  carbonic  or  sulphurous  acid  or  with  both  at  the 
same  time.  In  many  factories  the  alkalinity  is  lowered  nearly  to  a 
neutral  reaction,  while  others  consider  that  an  alkalinity  of  0.03- 
0.04  is  proper.  Here  also  it  is  better  to  fix  the  alkalinity  according 
to  the  behavior  of  the  sirup  in  the  later  stages  of  the  process.  If  the 
alkalinity  decreases  much  in  the  vacuum-pan,  the  alkalinity  of 

170 


CARBOXATAtlOX   AXD   FILTRATION.  171 

the  sirup  should  be  kept  high  enough  so  that  the  massecuite  as  well 
as  the  first  sugars  and  molasses  ("green  sirup")  will  show  a  distinct 
red  color  with  phenolphthalei'n.  If,  on  the  contrary,  the  sirup 
contains  much  free  alkali  and  no  lime  salts,  it  can  be  carbonatated 
almost  to  neutrality,  since  any  decrease  in  alkalinity  in  such  cases 
is  little  to  be  feared.  The  objection  attributed  to  high  alkalinity 
that  it  makes  the  sirup  work  up  harder  in  the  vacuum-pan  and 
that  it  increases  the  ash  in  the  sugar  is  unwarranted.  The  only 
thing  that  makes  the  pan  work  harder  is  when  the  alkalinity  is 
due  to  caustic  lime,  which  means  that  sucrates  will  be  present.  This 
cannot  be  within  alkalinity  of  0.03-0.05,  as  this  is  almost  invaria- 
bly from  combinations  of  carbonic  acid  with  the  alkaline  earths, 
ammonia,  or  organic  bases.  Moreover,  high  ash-content  is  not  a 
result  of  alkalinity.  Under  the  most  favorable  conditions,  when 
carbonatation  with  carbonic  or  sulphurous  acid  is  thorough,  the 
carbonates  and  sulphites  would  react  with  any  caustic  lime  and 
be  precipitated  in  considerable  quantity  as  lime  carbonate  or 
sulphite.  Thorc  would  be  at  most,  therefore,  0.03-0.05  part  of  lime 
in  100  parts  of  sirup,  which  corresponds  to  1.5—2.0  parts  total  ash, 
scarcely  perceptible  in  the  sugar.  Since  the  reactions  of  carbonic 
and  sulphurous  acids  with  lime  salts  are  never  complete,  especially 
if  filtration  immediately  follows  carbonatation,  a  small  amount  of 
lime  will  always  be  precipitated  by  further  carbonatation,  and 
consequently,  taking  into  consideration  the  influence  this  has  on 
the  sugar-yield,  it  is  hardly  wise  to  make  a  carbonatation  as  far 
as  the  neutral  point.  However,  this  is  of  little  consequence  in  its 
bearing  on  the  ash-content  of  the  sirup  in  comparison  with  the 
much  more  important  point  of  keeping  the  proper  temperature 
during  carbonatation,  and  above  all  things  a  good  filtration. 

The  sirup  which  is  pumped  out  of  the  evaporator  is  only  at  the 
temperature  corresponding  to  the  boiling-point  of  the  last  effect, 
that  is  70°  C.  (158°  F.).  Before  carbonatation  it  should  be 
brought  almost  to  boiling,  which  is  best  done  by  using  special 
exhaust-steam  heaters.  Direct-steam  injectors  are  of  no  use  here, 
as  they  would  dilute  the  sirup  too  much. 

The  carbonatation  of  the  sirup  is  best  done   continuously  in 


172  BEET-SUGAR  MANUFACTURE. 

one  tank,  pumping  the  sirup  through  it  and  at  the  same  time 
introducing  the  carbonic  or  sulphurous  acid  according  to  the 
alkalinity  required,  the  sirup  running  to  the  filters  at  the  same 
rate  that  it  is  pumped  in.  In  such  cases  it  is  advisable  to  add 
kieselguhr  (fossil  meal)  about  1  kilogram  per  cubic  meter  of  juice 
(8.34  Ibs.  per  1000  gals.)  The  carbonatation  tank  should  have  a 
stirrer  to  mix  in  the  kieselguhr  evenly.  Kieselguhr  can  always 
be  added  to  advantage  to  the  thickened  juice  of  the  first  runnings 
at  the  beginning  of  the  campaign  and  at  the  start  of  each  week's 
work,  as  the  juice  at  such  times  is  full  of  dirt  and  rust  from  the 
apparatus,  likewise  when  much  oil  has  to  be  used  in  the  evaporators 
owing  to  foaming. 

Ordinarily  lime  is  not  added  to  the  sirup,  it  being  quite  super- 
fluous if  the  thin  liquor  and  corresponding  uncarbonatated  sirup  is 
sufficiently  alkaline.  Such  sirups,  having  an  alkalinity  of  0.07-0. 15 
in  carbonatating  at  the  boiling  temperature,  give  sufficient  granular 
precipitate  to  enclose  the  scummy  material  so  that  usually  they 
filter  very  well.  If,  however,  the  sirup  is  very  slightly  alkaline, 
owing  to  carbonatating  too  far,  there  is  little  or  no  precipitate  and 
it  filters  badly. 

Sometimes  addition  of  a  little  milk  of  lime  helps,  but  it  seems 
that  sirup  coming  from  the  evaporator,  which  already  has  a  high 
alkalinity,  always  filters  better.  If  lime  is  added  to  the  sirup,  it 
will  affect  it  some  time  later  if  the  temperature  is  high,  and  con- 
tinuous carbonatation  is  not  applicable  in  such  cases  or  it  must  be 
done  differently. 

In  the  clarifying  and  later  working  up  of  sirup  it  is  of  no  conse- 
quence whether  carbonic  or  sulphurous  acid  is  used  in  carbonata- 
tion. Carbonatation  with  sulphurous  acid  has  the  advantage  that 
it  gives  lighter  sirups  and  sugars,  and  owing  to  the  small  quantity 
of  sulphites  retained  they  keep  better.  Indeed,  if  sulphurous  acid 
is  to  be  used  for  treating  beet-juices,  it  should  be  applied  only  to 
sirups,  and  here  its  use  is  strongly  to  be  recommended. 

The  same  apparatus  serves  for  sirup-filtration  as  for  thin  liquors, 
but  in  general  a  somewhat  higher  pressure  is  preferable  for  sirups, 
for  which  filter-presses  of  special  design,  with  wooden  chambers 


CARBONATATION    AND  FILTRATION.  173 

and  the  sand  filters  previously  described,  are  used.  The  sirup 
running  from  the  filters  in  the  beginning  always  comes  cloudy, 
and  is  returned  to  the  thin-liquor  carbonatation-tanks  till  it  runs 
clear  enough  for  the  sirup-tanks.  The  scums  which  collect  on  the 
cloths  cannot  be  sweetened  off,  so  presses  with  sweetening-off 
passages  are  as  little  in  use  as  in  thin-liquor  filtration.  Since, 
however,  these  scums  are  rich  in  sugar,  it  has  been  recommended 
to  return  them  to  the  carbonatation-tanks.  When  the  filter-cloths 
are  removed  they  likewise  are  full  of  sugary  sirup.  It  is  doubtful 
whether  it  is  advisable  to  soak  these  cloths  to  recover  this  sugar, 
as  the  sirup,  from  remaining  an  unavoidably  long  time,  is  always 
much  deteriorated.  As  a  rule  the  sugar-loss  in  scums  and  cloths 
is  so  small  that  it  is  not  worth  taking  into  consideration. 

In  most  cases  sirups  filter  fairly  well,  but  there  will  be  those 
which  filter  badly  if  at  all,  especially  those  heavier  than  60°  Brix 
(33°  Be.).  In  such  cases  it  is  advisable  to  carbonatate  and  filter 
the  so-called  intermediate  sirup  ("mittelsaft"),  that  is  the  sirup 
as  it  comes  out  of  the  effect  of  the  evaporator  preceding  the  last. 
This  sirup,  which  is  about  30°  Brix  (17°  Be.),  is  pumped  to  the 
carbonatation-tank  and  treated  there  in  the  manner  prescribed  for 
sirup  and  drawn  into  the  last  effect,  where  it  is  concentrated  to  the 
usual  density.  This  will  again  cloud  up  a  little,  but  the  bulk  of 
the  scum  is  now  filtered  out  of  it  and  very  efficiently,  so  that  a 
second  sirup-filtration  can  be  dispensed  with.  The  filtration  of 
the  intermediate  sirup  is  especially  advisable  when  the  sirup 
deposits  much  scale  in  the  multiple  effect,  since  the  scale  is  formed 
principally  from  this  scum,  which  precipitates  out  from  the  thin 
liquor  while  concentrating,  and  sticks  to  the  tubes. 

Sometimes  this  intermediate  sirup  is  clarified  in  a  closed  filter 
(using  gravel  or  bone-black  or  by  a  closed  filter-press)  so  introduced 
between  the  last  effect  and  the  one  next  to  the  last  that  the  sirup 
must  pass  through  it.  Leaving  out  of  consideration  that  this 
arrangement  is  quite  inconvenient  and  that  the  pressure-difference 
is  often  insufficient  for  filtering,  obviously  carbonatation  is  wanting 
before  filtering.  However,  in  many  factories  the  juice  is  carbona- 
tated  in  the  evaporator  itself,  by  passing  sulphurous  acid  into  the 


174  BEET-SUGAR   MANUFACTURE. 

juice  while  boiling  inside,  but  this  kind  of  carbonatation  is  by  no 
means  easy  to  control  and  is  not  therefore  to  be  recommended. 

There  are  no  sure  methods  of  determining  whether  a  sirup  has 
the  right  composition  to  work  up  easily.  A  juice  or  sirup  of  high 
purity  will  surely  work  up  well,  but  with  beets  of  poor  quality 
where  the  sirup  only  has  a  purity  of  90  or  under,  neither  chem- 
ical analysis  nor  color  has  any  criterion  on  this  point.  Often 
there  is  a  belief  that  the  amount  of  lime  present,  that  is  the  content 
of  lime  salts,  is  a  measure  of  how  the  j  uice  will  work  up,  but  the 
truth  is,  everything  depends  on  the  nature  of  these  lime  salts. 
Sometimes  an  excessive  quantity  of  these  salts  is  to  a  certain 
extent  a  sign  that  juice  of  bad  beets  must  be  improved  as  much 
as  possible  by  energetic  treatment  with  lime.  Color  is  no  guide 
to  the  quality  of  a  sirup. 

It  certainly  would  be  quite  wrong  to  conclude  that  a  light- 
colored  sirup,  especially  one  which  had  been  bleached  with  all 
sorts  of  chemicals  and  made  weakly  acid  with  sulphurous  acid, 
was  better  than  a  darker  sirup,  and  that  better  products  could  be 
made  from  the  former. 

If  the  thin  liquor  has  been  properly  treated  according  to  the 
directions  given,  the  best  possible  sirup  under  the  circumstances 
will  be  obtained,  but  it  is  surely  not  practicable  to  get  a  good  clarifi- 
cation of  sirup  if  the  thin  liquor  has  been  carelessly  treated,  as 
mistakes  made  in  the  thin-liquor  treatment  cannot  be  remedied 
later  in  the  sirup. 


CHAPTER  XV. 
SUGAR-BOILING. 

AFTER  the  sirup  has  been  filtered,  it  is  evaporated  to  grain  in  a 
vacuum-pan.  This  apparatus  should  serve  both  for  evaporation 
of  the  sirup  and  for  crystallization  of  the  sugar,  and  consequently 
both  of  these  requirements  must  be  satisfied,  but  the  chief  essential 
is  that  there  should  be  a  proper  crystallization  of  the  sugar.  In 
general,  this  vacuum  apparatus  is  similar  in  shape  and  arrangement 
to  that  previously  described,  except  that  certain  changes  are  made 
necessary  in  order  to  concentrate  liquids  which,  thick  and  viscous 
at  the  start,  become  at  the  last  a  pasty  mass* .  Usually  vacuum- 
pans  are  vertical  with  conical  bottoms.  The  heating-surfaces  are 
coils  placed  one  over  the  other  or  intertwined,  heating-tubes  of  Lyra 
type  arranged  horizontally.  Sometimes  short  and  wide  tubes 
or  vertical  tubes  are  built  into  heating-chambers  arranged  for 
introduction  of  steam  and  carrying  off  condensed  water.  The 
horizontal  vacuum-pans  always  are  of  a  trunk  shape,  arranged 
•like  evaporating-pans,  and  have  a  single  bottom  suitably  inclined 
towards  the  discharge-gate.  All  heating-surfaces  are  placed  as 
low  as  possible,  so  that  they  are  covered  with  sirup  from  the 
beginning. 

Iron  is  the  metal  very  frequently  used  for  making  these  heating- 
tubes,  it  having  the  advantage  over  brass  and  copper  that  it  is 
less  attacked  by  ammonia-vapors,  while  the  disadvantage  that 
it  is  a  poorer  conductor  of  heat  of  is  less  consequence  here  because 
the  amount  of  heat  to  be  transmitted  to  the  juice  is  of  itself  very 
inconsiderable.  In  the  vacuum-pan,  ammonia-vapors  act  more 
injuriously  upon  the  heating-tubes  than  in  the  evaporating-pans, 

175 


176  BEET-SUGAR  MANUFACTURE. 

because  with  the  former,  toward  the  end  of  the  operation,  there  is 
less  movement  of  hot  vapors,  and  hence  these  ammonia-vapors 
move  slower  and  may  collect  in  certain  places. 

The  discharge-gate  of  vacuum-pans  is  usually  a  cone.  When 
massecuites  are  boiled  down  with  considerable  sirup,  so  that  a 
relatively  thin  liquor  remains,  the  discharge-opening  is  closed  with 
a  valve.  The  double  bottom,  which  was  formerly  quite  universally 
used,  is  now  usually  dispensed  with,  although  it  does  accomplish  a 
certain  desirable  effect,  because  with  such  an  arrangement  bubbles 
of  steam  are  formed  down  in  the  lower  layers,  and  this  is  favorable 
to  the  movement  of  the  massecuite  and  facilitates  the  boiling 
and  crystallization.  As  a  method  of  heating,  however,  the  double 
bottom  is  not  very  efficient,  the  heating  coefficient  being  very  low. 

The  equipment  of  vacuum-pans  must  otherwise  be  such  that 
the  pan  man  can  easily  control  his  boiling  and  readily  detect 
anything  wrong  and  remedy  the  evil.  The  sample  or  proof-stick 
should  be  correctly  placed,  where  there  is  sufficient  movement  of  the 
massecuite  to  insure  taking  a  proof  which  shall  represent  the 
average  content.  There  should  be  an  abundance  of  sight-glasses 
in  the  sides,  so  arranged  that  the  interior  of  the  pan  can  be  readily 
seen.  The  thermometer  and  its  stem  must  penetrate  sufficiently 
deep.  A  mercury  gauge  should  be  provided  to  show  the  amount 
of  vacuum.  The  charging  valves  must  be  large  and  conveniently 
arranged.  The  charging  pipe,  whether  inside  or  outside,  must 
lead  to  the  bottom  of  the  apparatus  and  end  in  a  suitable 
distributing  ar/angement.  For  heating,  steam  of  high  or  low 
tension,  as  required,  must  be  used  and  the  corresponding  con- 
nections to  the  main  valves  should  be  easily  made.  The  sugar- 
boiler  must  be  able  to  read  the  steam-pressure  both  as  it  leaves 
'and  enters  the  heating  system  by  a  gauge.  Of  course  the  heat- 
ing system  must  be  equipped  with  pipes  for  conducting  away 
condensation-water,  and  suitably  arranged  for  leading  off 
ammonia-vapors.  Special  valves  should  be  provided  for  draw- 
ing  in  cold  or  hot  water.  It  is  very  practical  to  introduce  a 
perforated  coil,  or  a  similar  distributing  arrangement,  in  order 
to  be  able  to  introduce  live  steam  directly  into  the  massecuite 


177 

and  sot  it  in  motion.  After  the  strike  is  down  this  steam  may  bo 
carried  through  special  pipes  and  used  for  evaporating. 

The  size  of  vacuum-pans  is  very  variable.  A  large  apparatus 
naturally  demands  less  attention  than  several  small  pans  having 
the  same  capacity.  On  the  other  hand,  taking  into  consideration 
the  work  of  the  factory  as  a  whole,  and  in  particular  that  of  the 
evaporation  apparatus,  as  already  mentioned,  it  is  less  advanta- 
geous to  have  but  one  large  vacuum-pan;  for  when  this  is  started 
it  requires  more  steam  from  the  evaporators  than  the  latter  can 
give.  As  the  process  proceeds,  less  sirup  will  be  drawn  in  and  less 
steam  will  be  required,  so  that  finally  none  at  all  is  used,  as  the 
sirup  gets  thick.  Consequently  it  is  necessary  that  every  factory 
should  have  at  least  two  boiling-pans  of  suitable  size,  in  order  to 
take  care  of  the  sirup  systematically  and  make  the  use  of  steam 
uniform. 

With  regard  to  the  size  of  the  heating-surface  in  vacuum-pans 
there  is  no  definite  rule  to  give;  it  is  not  possible  to  calculate  it  as 
in  the  case  of  the  multiple  effect,  since  the  conditions  affecting 
the  transference  of  heat  are  so  varied  during  the  boiling  process, 
and  at  different  times  quite  different  amounts  of  water  are  to 
be  evaporated.  In  this  apparatus  evaporation  is  only  a  means 
to  the  chief  end,  namely,  the  crystallization  of  the  sugar.  Since 
heating-surface  in  excess  cannot  do  any  harm  if  placed  at  the  bot- 
tom of  the  apparatus  and  under  no  conditions  does  it  influence  the 
circulation  of  the  massecuite,  it  is  well  to  make  this  large.  ^It  is 
then  always  possible,  and  particularly  at  the  start,  to  conduct  the 
evaporation  quickly  and  make  use  of  low-pressure  steam  for 
evaporating.  The  amount  of  heat  conveyed  to  the  boiling  mass, 
or  in  other  words  the  evaporation,  in  this  case  does  not  depend 
upon  the  size  of  the  heating-surfaces,  but  upon  the  amount  and 
tension  of  the  steam  admitted  into  the  heating-space.  Since  with 
large  heating-surfaces  only  a  part  of  this  steam  is  really  active, 
it  is  advisable,  when  possible,  to  construct  the  heating  system 
with  several  compartments  each  of  which  is  provided  with  inde- 
pendent pipes  for  introduction  of  steam  and  conducting  away 
condensation-water,  these  compartments  being  heated  as  they  are 


178  .         BEET-SUGAR  MANUFACTURE. 

needed.  In  all  cases  it  should  be  possible  to  regulate  the  evapora- 
tion by  means  of  the  valves,  so  that  the  proper  conditions  for  favor- 
able crystallization  of  the  sugar  shall  prevail.  Vacuum-pans  with 
a  capacity  of  20,000  to  50,000  kilograms  (20  to  50  long  tons),  which 
is  the  common  size  now  chosen,  have  a  heating-surface  of  from 
80  to  150  square  meters  (860-1600  sq.  ft.). 

The  question  as  to  best  construction  of  the  boiling  apparatus 
and  of  heating-surfaces  is  one  that  is  hard  to  answer.  A  skillful 
sugar-boiler  will  be  able  to  produce  good  sugar  in  any  apparatus 
in  which  the  heating-surfaces  are  active  and  do  not  hinder  the 
circulation.  The  fact  that  a  sugar-boiler  gets  bad  results  in  a  new 
apparatus,  while  he  has  been  doing  well  with  an  old  one  to  which 
he  has  become  accustomed,  is  not  conclusive  proof  that  the  new 
vacuum-pan  is  bad.  Boiling  in  grain  is  an  art  which  is  usually 
learned  entirely  experimentally  and  must  be  learned  anew  for  a 
differently  constructed  apparatus  and  for  every  masscuite  of  dif- 
ferent consistency. 

The  art  of  boiling  to  grain  consists  in  forming  the  necessary 
number  of  crystals  in  the  thickened  sirup  and  then  in  further 
boiling,  allowing  only  these  particular  crystals  to  grow  without 
forming  a  perceptible  amount  of  new  ones.  The  operator  accom- 
plishes this  by  hazarding  a  conclusion  as  to  the  concentration  of 
the  sirup  by  the  outward  appearance  of  the  sample  which  he 
takes  from  the  apparatus.  It  would  be  quite  useless  to  attempt 
to  describe  here  just  how  the  boiler  arrives  at  the  proper  con- 
clusion. It  is  only  possible  to  acquire  this  skill  by  practical  ex- 
perience, and  every  individual  has  his  own  peculiar  method. 

The  important  point  with  regard  to  the  art  of  sugar-boiling  in 
grain  and  which  serves  for  the  judgment  of  the  correctness  or 
inaccuracy  of  individual  methods  is  a  knowledge  of  the  actual 
processes  which  are  taking  place  during  the  operation. 

For  crystals  to  form  in  a  sugar-solution  and  for  these  crystals 
to  grow,  it  is  necessary  that  the  solution  become  "  supersaturated.'' 
A  solution  containing  sugar  is  "saturated"  if,  when  kept  at  a 
uniform  temperature,  it  can  neither  dissolve  any  more  sugar  nor 
form  sugar-crystals.  The  higher  the  temperature  of  the  solution, 


SUGAR-BOILING.  179 

the  more  sugar  can  be  dissolved  by  each  part  of  water  present. 
If  the  solution  is  evaporated  to  a  smaller  volume  while  at  the 
temperature  at  which  it  is  saturated,  the  sugar  does  not  imme- 
diately crystallize  out,  but  for  the  time  being  it  remains  dissolved 
and  the  solution  is  then  said  to  be  "  supersaturated."  The  purer 
the  saturated  sugar-solution  and  the  greater  the  number  of  crys- 
tals there  are  in  it  which  have  already  started  to  form,  the  more 
rapid  is  the  separation  of  the  excess  of  sugar  over  the  amount 
required  to  saturate  the  solution  and  the  more  rapid  is  the  growth 
of  the  deposited  crystals."^  Impure  sugar-solutions  require  con- 
siderable more  time  for  the  deposition  of  crystals;  they  must  be 
much  more  strongly  supersaturated  before  they  will  deposit 
crystals  or  allow  them  to  grow,  and  this  is  proportional  to  the 
amount  of  non-sugars  that  these  solutions  contain. 

If  we  designate  by  S  the  amount  of  sugar  dissolved  in  one  part 
of  water  at  a  definite  temperature  when  the  solution  is  saturated, 
and  by  Si  that  amount  which  at  the  same  temperature  is  dissolved 
in  the  same  amount  of  water  in  a  supersaturated  solution,  then  the 

^    S 
ratio  C  =-77  is  called  the  supersaturation-coefficient.    It  represents 

o 

how  many  times  as  much  sugar  there  is  dissolved  in  the  super- 
saturated solution  as  in  a  saturated  solution  at  the  same  temperature. 
This  coefficient  of  supersaturation  is  of  fundamental  importance  in 
the  crystallization  of  the  sugar,  whether  the  latter  be  brought  about 
by  means  of  evaporation  or  by  the  working  up  of  the  massecuite. 
While  all  other  conditions  which  affect  the  crystallization  of  the 
sugar,  such  as  the  viscosity,  change  with  the  temperature,  this  super- 
saturation-coefficient  is  independent  of  the  temperature'.  It  makes 
no  difference,  therefore,  whether  the  boiling-down  or  other  process 
used  to  effect  the  crystallization  is  carried  out  at  a  high  or  a  low 
temperature,  the  most  favorable  coefficient  of  supersaturation  for 
the  formation  of  new  crystals  and  the  growth  of  those  already 
formed  is  always  the  same  (within  the  practical  limits  of  temperature- 
changes)  for  sirups  and  juices  of  equal  purity,  although  it  varies 
with  the  purity,  as  has  already  been  stated.^  Furthermore,  the 
coefficient  of  supersaturation  must  be  greater  for  the  formation  of 


180  BEET-SUGAR  MANUFACTURE. 

the  grain  and  smaller,  on  the  other  hand,  when  the  crystallization 
is  favored  by  the  presence  of  crystals  in  the  solution. 

For  a  well-regulated  crystallization  it  is  important  that  the 
supersaturation  and  the  temperature  which  determines  it  should 
be  the  same  at  all  points  of  the  crystallizing  mass.  The  super- 
saturation  changes  during  boiling  at  first  take  place  at  the  heating- 
surfaces,  on  account  of  evaporation,  so  that  at  these  places  stronger 
supersaturated  solutions  are  readily  formed  which  are  likely  to 
give  rise  to  the  formation  of  small  crystals.  On  the  other  hand, 
at  the  places  where  the  fresh  sirup  enters,  the  supersaturation  is 
likely  to  be  entirely  eliminated  with  the  solution  of  the  crystals 
already  formed,  unless  the  sirup  is  immediately  disseminated 
throughout  the  entire  mass  and  mixed  with  the  supersaturated 
sirup  which  surrounds  the  crystals. ^Consequently  the  greatest 
stress  must  be  laid  upon  the  importance  of  keeping  a  most 
thorough  circulation  of  the  mass  in  the  vacuum-pan.  The  con- 
struction of  the  apparatus  and  the  heating-coils  should  not  offer 
any  especial  hindrance  to  such  circulation;  no  method  of  con- 
struction, however,  can  bring  about  currents  in  the  juice,  but 
mechanical  forces  are  required  for  this  which  are  developed  during 
the  boiling  by  the  ascending  bubbles  of  water-vapor.  As  a 
matter  of  fact  the  evolution  of  these  bubbles  of  steam  is  the 
slightest  at  that  stage  where  it  is  most  desirable  that  there  should 
be  a  circulation  of  the  mass,  namely,  at  the  end  of  the  boiling. 
Arrangements  by  means  of  which  at  any  time  a  regular  motion  can 
be  imparted  to  the  mass  have  proved  very  advantageous.  Stirring- 
apparatus,  screws,  etc.,  have  been  found  very  satisfactory  in  this 
respect  for  "the  boiling-apparatus  used  for  after-products.  In  the 
case  of  sirup-boiling  such  arrangements  have  not  been  used  to 
any  extent,  largely  because  the  available  space  is  too  limited, 
particularly  in  the  older  forms  of  apparatus;  in  the  newer  types 
stirring-arrangements  are  frequently  found.  The  motion  brought 
about  by  introduction  of  direct  steam  is  very  satisfactory.  The 
bubbles  of  steam  rising  from  the  lower  portions  of  the  compart- 
ments stir  the  mass  in  all  places  and  particularly  at  the  heating- 
surfaces,  which  they  can  spread  over  much  more  satisfactorily  than 


SUGAR-BOILIX(i.  181 

could  any  stirring-apparatus,  so  that  all  local  supersaturation  or 
overheating  is  avoided.  Consequently  it  is  easy  to  avoid  the 
formation  of  a  fine  grain,  especially  when  the  massecuite  is  kept 
in  motion  in  this  way  by  bubbles  of  steam. 

In  order  to  distribute  the  entering  sirup  throughout  the  mass 
as  quickly  as  possible,  it  is  introduced  at  the  bottom  and  in  fine 
streams  so  that  it  will  rapidly  mix  with  the  mother-sirup,  since  it 
rises  at  once  on  account  of  its  lighter  specific  gravity.  This  mixing 
is  accelerated  considerably  if, the  sirup  as  it  enters  is  very  hot,  with 
a  temperature  higher  than  that  of  the  boiling  mass.  As  the  sirup  r 
enters  the  vacuum-pan,  a  considerable  quantity  of  steam-bubbles 
is  suddenly  generated,  thus  accomplishing  a  rapid  mixture  with 
the  remaining  contents  of  the  apparatus.  The  sirup  should  not  be  jZ 
allowed  to  enter  at  a  temperature  lower  than  the  boiling-point  in 
the  vacuum-pan,  for  it  will  then  mix  but  slowly,  while  the  massecuite 
will  be  cooled  with  the  probability  of  forming  a  fine  grain. 

For  the  formation  of  grain  in  the  vacuum-pan,  therefore,  it  is 
necessary  that  the  sirup  should  be  supersaturated.  As  soon  as 
the  supersaturation  has  reached  a  certain  degree,  crystals  begin  to 
separate.  It  has  been  found  advantageous  to  start  the  formation 
with  the  shock  brought  about  by  a  sudden  introduction  of  the  sirup. 
The  greater  the  supersaturation  of  the  juice  and  the  greater  the 
motion,  the  quicker  and  richer  will  be  the  crystal  formation.  Under 
otherwise  similar  conditions  it  is  necessary,  therefore,  to  thicken 
the  sirup  less  and  to  draw  in  less  in  proportion  as  it  is  desired  to 
form  less  grain.  However,  the  extent  of  the  supersaturation  may 
be  quite  different  for  the  production  of  equal-sized  grain,  because  in 
the  case  of  continuous  motion,  which  is  brought  about,  for  instance, 
by  frequent  opening  of  the  sirup-valve,  it  is  possible  .to  form  many 
crystals  in  very  slightly  supersaturated  solutions,  and  conversely 
by  infrequent  introduction  of  the  juice  it  is  possible  to  form  but 
little  grain  in  strongly  supersaturated  solutions.  The  number  1.2 
may  be  regarded  as  the  lowest  practical  value  for  the  supersaturation- 
coefficient  for  the  formation  of  grain  in  sirups  of  from  90  to  92 
purity;  at  a  less  supersaturation  it  takes  too  long  before  sufficient 
grain  is  produced,  and  there  is  always  danger  that  the  crystals 


182  BEET-SUGAR  MANUFACTURE. 

already  formed  will  be  redissolved  by  the  introduction  of  fresh 
juice.  The  highest  degree  of  supersaturation  is  with  a  coefficient 
of  1.5  to  1.6,  for  when  more  supersaturated  too  many  crystals  will 
be  obtained  by  a  single  draught  of  the  juice. 

When,  in  one  way  or  another,  sufficient  grain  has  been  formed, 
further  boiling  is  conducted  in  such  a  way  that  only  these  crystals 
grow  and  no  others.  As  long  as  the  crystals  remain  small  and  in 
consequence  possess  relatively  small  surfaces  for  the  deposition  of 
the  crystallizing  sugar,  it  is  necessary  to  keep  the  surrounding 
sirup,  the  mother-liquor,  but  slightly  supersaturated;  for,  as  this 
sirup  lias  still  approximately  the  purity  of  the  original  thick  juice, 
it  retains  the  property  of  forming  new  crystals  at  a  supersaturation 
of  1.2  by  the  motion  brought  about  by  the  entrance  of  the  sirup. 
During  this  stage  of  the  boiling,  therefore,  the  extent  of  the  super- 
saturation  should  not  exceed  a  coefficient  of  1.2;  it  is  safer  not  to 
even  reach  this  limit. 

The  boiling  from  this  point  on  can  be  conducted  in  two  ways, 
either  with  an  uninterrupted  or  with  an  intermittent  charging  of 
juice.  In  the  former  case  the  juice- valve  is  so  set  that  exactly 
the  right  quantity  of  thick  juice  will  be  introduced  in  order  to  keep 
the  mother-sirup  permanently  at  the  prescribed  uniform  super- 
saturation.  The  coefficient  of  supersaturation  1.1  is  to  be  recom- 
mended, but  at  all  events  it  should  not  be  greatly  exceeded  at  the 
start.  In  the  case  of  periodic  introduction  of  the  juice,  the  valve 
is  opened  when  the  coefficient  of  supersaturation  has  risen  to 
approximately  1.2  and  enough  juice  is  drawn  in  to  nearly  compensate 
the  supersaturation,  bringing  the  coefficient  down  to  nearly  1.0. 
On  no  account  should  the  mother-sirup  be  diluted  to  a  point  below 
the  saturation-point,  as  otherwise  the  crystals  already  formed  will 
be  redissolved.  As  a  general  rule  for  both  methods  of  feeding  it 
may  be  said  that  in  the  case  of  slow  boiling  the  upper  limit  of 
supersaturation  must  be  kept  lower  than  with  rapid  boiling. 

Only  in  case  too  many  crystals  have  been  formed  in  the  grain, 
or  when  later  on  fine  crystals  have  been  produced  through  a  faulty 
conduct  of  the  operation,  should  enough  sirup  be  introduced 
to  make  the  mother-sirup  undersaturated  so  that  the  excess  of 


SUGAR-BOILING.  183 

crystals  will  redissolve.  Frequently  such  a  dilution  is  brought 
about  not  by  using  sirup,  particularly  when  it  is  very  thick  and 
concentrated,  but  by  the  injection  of  hot  water,  and  this  is  some- 
times necessary,  chiefly  towards  the  end  of  the  boiling,  in  order  to 
make  a  clean  massecuite. 

During  the  progress  of  the  boiling  the  sugar-crystals  are  con- 
stantly growing  and  the  purity  of  the  mother-sirup  becomes  less.  It 
is  therefore  not  only  permissible  but  even  regarded  as  advantageous 
to  bring  the  supersaturation-coefficient  to  1.2  and  even  higher,  until 
at  the  last  drawing  of  the  juice  it  reaches  the  value  of  about  1.3. 

The  art  of  boiling  now  consists  only  in  being  able  to  find  out 
the  proper  coefficient  of  supersaturation  and  to  maintain  it  in  the 
mass  by  the  external  tokens,  such  as  the  string-proof  and  the  viscos- 
ity of  the  massecuite, and  by  noting  the  temperature  and  the  trans- 
parency of  the  crystals  surrounded  by  sirup.  Most  operators  boil 
with  intermittent  feeding  of  sirup,  because  this  method  is  safer 
when  the  vacuum  and  steam-pressure  are  variable,  as  is  usually  the 
case.  When,  on  the  other  hand,  these  conditions  are  constant  and 
the  juice  that  is  being  fed  in  is  of  uniform  density,  it  is  simpler  to 
inject  this  juice  uninterruptedly. 

The  steam  must  be  so  regulated  that  the  evaporation  does 
not  take  place  too  rapidly,  and  that  after  each  introduction 
of  the  sirup  the  sugar  actually  has  time  to  deposit  upon  the 
crystals  present  while  the  purity  of  the  mother-liquor  sinks 
regularly.  The  duration  of  the  boiling  can  be  shortened  only  at 
the  expense  of  the  yield,  or  by  subsequent  working  up  of  the 
massecuite  in  crystallizers  or  coolers  and  so  doing  what  was  omitted 
previously.  The  rule  should  hold  that  boiling  in  grain  should  be 
conducted  as  slowly  as  possible,  or  at  all  events  one  boiling  should 
require  not  less  than  six  or  eight  hours  for  its  completion,  and  those 
vacuum-pans  which  make  it  possible  to  boil  in  less  time  should  not 
be  regarded  as  superior,  because  it  is  not  possible  to  replace  the 
favorable  action  of  time  by  any  peculiar  method  of  construction. 
hi  order  to  offset  the  temptation  of  boiling  too  rapidly,  which 
occurs  when  using  apparatus  with  large  heating-surfaces,  it  is  advis- 
able to  heat  such  forms  of  vacuum  apparatus  with  steam  of  as  low 


184  BEET-SUGAR  MANUFACTURE. 

pressure  as  possible,  this  being  also  economical  both  with  regard 
to  steam-consumption  and  sugar-loss. 

The  size  of  the  vacuum-pan  exerts  no  influence  upon  the  quality 
of  the  boiling.  It  is  possible  to  get  just  as  good  crystallization  in  a 
small  apparatus  as  in  a  large  one  if  both  are  properly  constructed. 
The  chief  point  is  not  to  begin  the  formation  of  the  grain  with  the 
apparatus  too  full.  The  pan  should  not  be  filled  to  more  than 
from  one-quarter  to  one-third  of  its  total  capacity,  so  that  the 
crystals  have  time  to  grow  during  the  further  boiling. 

A  properly  boiled  massecuite,  containing  no  excess  of  molasses- 
sirup,  should  yield  a  mother-liquor  of  from  80  to  82  purity  If 
the  duration  of  the  boiling  is  continued  for  a  very  long  time,  it  is 
possible  to  diminish  to  a  considerable  extent  this  purity,  particularly 
if  the  apparatus  be  provided  with  a  suitable  stirring-arrangement. 
It  appears  questionable,  however,  whether  it  is  desirable  to  produce 
such  an  extent  of  sugar-crystallization  in  a  vacuum  without  the 
further  introduction  of  sirup,  and  it  is  doubtful  whether  the  further 
working  up  of  the  massecuite  may  not  be  more  advantageously 
conducted  in  special  crystallizers. 

After  the  last  introduction  of  the  sirup  the  finishing  of  the  masse- 
cuite begins.  The  manner  in  which  this  should  be  carried  out  de- 
pends upon  the  way  the  later  processes  are  to  be  conducted.  If  the 
massecuite  is  to  be  discharged  into  large  or  small  tanks,  according 
to  what  is  now  regarded  as  the  old-fashioned  method,*  it  is  boiled 
down  until  very  hard  and  close,  with  a  water-content  of  only  about 
5  per  cent.,  or  less.  This  carries  the  supersaturation  of  the  mother- 
sirup  so  far  at  the  end  that  even  in  the  boiling-pan,  or  at  all  events 
as  soon  as  it  is  discharged,  a  large  number  of  small,  new  crystals 
are  formed  which,  as  the  massecuite  cools  in  the  tanks,  cause  all 
the  sugar  that  crystallizes  out  to  deposit  upon  them  or  upon  the 
larger  crystals.  Only  a  small  part  of  these  crystals  which  are 
formed  at  the  last  are  of  sufficient  size  to  be  retained  in  the  centrif- 
ugal machines;  the  greater  part  are  so  small  that  they  pass  through 
the  strainer  with  the  sirup.  The  reason  why  it  is  desirable  to 
form  these  crystals  in  the  vacuum-pans  is  not  so  much  to  in- 
crease the  yield  as  to  obtain  a  satisfactory  working  of  the  cen- 

*  "  Cold  purging"  method. 


SUGAR-BOILING.  1  ^~, 

trifugals.  If  the  massecuite  were  emptied  out  in  a  softer  con- 
dition, there  would  be  a  formation  of  a  mass  of  tiny  crystals  in 
the  tank  so  great  in  number  that  they  would  scarcely  permit  any 
further  growth.  The  mother-sirup  would  consequently  be  com- 
pletely filled  with  a  fine  meal  which  would  make  the  centrifugal 
work  difficult  if  not  impossible.  This  fine  crystal  meal  deposits 
upon  the  large  crystals  or  upon  the  strainer  in  the  centrifugal, 
forming  a  film  which  is  impenetrable  to  the  sirup.  When  the  masse- 
cuite is  boiled  stiff,  there  are  fewer  of  these  small  crystals  formed, 
and  they  are  then  large  enough  so  that  they  do  not  form  a  film, 
but  in  so  far  as  they  are  not  retained  between  larger  crystals 
are  readily  thrown  off  by  the  centrifugals. 

For  the  ordinary  direct  mixing  method*  the  massecuite 
must  also  be  boiled  down  stiff  for  similar  reasons.  Consequently 
this  method  does  not  increase  the  sugar-yield,  but  frequently 
it  is  found  to  have  exactly  the  opposite  effect.  The  advantage 
gained  by  this  method  of  work  lies  in  the  saving  of  labor  and  its 
cleanliness. 

An  appreciable  increase  in  the  yield  can  be  brought  about  only 
by  the  new  method  of  working  up  the  massecuite  in  crystallizers 
in  which  the  cooling  and  concentration  of  the  mother-sirup  are 
carefully  regulated.  In  this  case  it  is  extremely  important  that 
the  massecuite  should  not  be  boiled  in  such  a  way  that  new  crystals 
will  be  formed  in  addition  to  the  large  ones  that  are  already  present. 
Consequently,  even  at  the  end  of  the  boiling,  the  supersaturation- 
coefficient  should  not  exceed  1.3.  Since  the  mother-sirup,  after  the 
last  injection  of  the  sirup,  already  has  approximately  this  coef- 
ficient, it  would  be  useless  to  carry  the  boiling  further  if  resource 
could  not  be  had  to  some  other  means.  After  the  last  addition  of 
the  juice  a  little  of  the  hot  molasses,  the  puiging  of  a  previous 
boiling  or  from  the  crystallizers,  is  injected  into  the  pan.  Thereby 
the  mother-sirup  becomes  diluted,  and,  if  necessary,  even  to  such 
an  extent  that  any  fine  crystals  which  may  have  been  formed 
n -dissolve  and  the  boiling  can  then  be  continued  slowly.  When 
the  gupersaturat  ion-coefficient  of  the  mother-sirup  has  again  risen 
to  1.3,  in  every  case  more  sirup  is  added  and  this  boiling  with  sirup 
*  "  Hot  purging"  method. 


186  BEET-SUGAR  MANUFACTURE. 

continued  for  from  one  to  two  hours.  The  longer  such  boiling  is 
continued,  the  more  sugar  will  be  deposited  upon  the  crystals 
Since  the  movement  of  the  mass  is  at  this  point  very  slight,  owing 
to  the  slow  evaporation,  any  arrangement  for  moving  the  mass  is 
very  useful,  particularly  when  this  is  accomplished  by  the  intro- 
duction of  steam. 

The  sugar  which  crystallizes  out  upon  the  crystals  already 
present  during  the  boiling  with  sirup  does  not  originate  in  the 
purgings  added,  but  comes  solely  from  the  mother-sirup,  and 
was  in  it  before  the  beginning  of  the  boiling,  the  purity  being 
80  or  over.  The  sirup  which  is  added  invariably  has  a  lower 
degree  of  purity,  and  at  the  conclusion  of  the  work  in  the  crys- 
stallizers  it  is  again  thrown  off  with  the  same  purity  at  which 
it  entered  the  boiling-pan.  In  the  vacuum-pan  it  is  used  as  a 
diluent  to  the  massecuite,  thereby  lengthening  the  boiling  opera- 
tion; it  also  makes  the  massecuite  work  better,  both  in  the  vacuum- 
pan  and  in  the  crystallizer,  by  increasing  the  amount  of  the 
mother-sirup. 

The  difficulty  of  educating  good  sugar-boilers  and  exerting  a 
control  over  them  has  caused  the  construction  of  a  special  form 
of  control  apparatus,  with  the  aid  of  which  the  boiling  can  be  carried 
out  with  greater  certainty  than  by  judging  from  not  very  trust- 
worthy outer  indications.  This  control  apparatus  depends  upon 
the  principle  that  the  boiling-point  of  a  sugar  solution  or  sirup 
stands  in  an  entirely  definite  relation  to  the  concentration.  The 
boiling-point  of  a  sirup  is  higher  in  proportion  to  the  amount  of 
non-sugars  that  it  contains  and  inversely  proportional  to  the 
amount  of  water.  For  sirups  of  equal  purity  the  rise  in  boiling.- 
point  with  decrease  in  the  amount  of  water  present  is,  however, 
always  the  same,  so  that  it  is  possible  to  prepare  tables  applicable 
to  all  cases  for  the  juices  and  sirups.  The  boiling-point  is  not 
influenced  by  the  fact  that  crystals  are  present  in  it,  hence  the 
boiling-point  of  a  massecuite  is  always  the  same  as  that  of  the 
mother-liquor  which  surrounds  the  crystals.  Again,  the  depth  of 
liquid,  which  is  considerable  toward  the  last  of  the  boiling,  does  not, 
as  far  as  the  thermometer  will  show,  influence  the  boiling-point 


SUGAR-BOILING.  187 

appreciably  if  care  is  taken  that  the  mass  is  kept  sufficiently  in 
motion. 

If;  by  means  of  a  thermometer,  the  boiling-point  of  the  sirup 
in  a  vacuum-pan  (the  mother-sirup)  be  determined  and  the  vacuum 
also  read  by  means  of  a  vacuum-gauge,  it  is  possible,  with  the  help 
of  the  tables  given  in  the  supplement  to  this  book,  to  determine 
the  boiling-point  of  water  at  the  vacuum  given.  Then  by  sub- 
tracting this  from  the  reading  of  the  thermometer  it  is  easy  to 
determine  the  rise  in  boiling-point  which  has  been  brought  about 
by  the  sirup.  From  the  above  data,  with  the  aid  of  the  boiling- 
point  tables,  it  is  a  simple  matter  to  calculate  the  amount  of  water 
present  in  the  sirup  in  question. 

Owing  to  the  construction  of  the  vacuum-pan,  the  immediate 
practical  utilization  of  the  result  is  attendant  with  more  or  less 
difficulty.  The  determination  of  the  amount  of  water  present  (or 
the  amount  in  degrees  Brix  in  the  case  of  an  incomplete  apparatus) 
is  of  itself  of  but  very  little  assistance  in  the  factory.  Separate 
tables  should  show  the  amount  of  water  that  the  sirup  must 
have  for  even'  particular  sirup,  and  for  the  swpersaturation  at  the 
particular  point  of  the  boiling;  and  when  these  are  graduated 
on  a  suitable  scale,  the  boiling  can  be  carried  out  without 
difficulty.  It  is  much  more  simple  to  have  the  control  appa- 
ratus show  directly  upon  the  scale  the  temperature  that  the  masse- 
cuite  should  have  at  every  stage  of  the  process.  This  latter  con 
struction,  which  permits  the  results  to  be  read  off  with  the 
greatest  readiness,  is  especially  suited  for  the  boiling  down  of  the 
first  massecuite. 

With  the  aid  of  such  an  apparatus  any  trustworthy  workman 
can  learn  in  a  short  time  how  to  conduct  the  boiling  and  make  uni- 
formly good  sugar.  This  control  is  also  particularly  useful  for  the 
superintendent  or  manager  of  the  plant.  When  the  ordinary 
method  is  being  used  any  one  who  does  not  remain  constantly  at 
the  boiling-pan  or  who  has  not  served  a  thorough  apprenticeship 
can  tell  very  little,  if  anything,  with  regard  to  whether  at  any  given 
time  the  boiler  is  conducting  the  operation  properly;  consequently  in 
many  factories  the  sugar-boiler  is  an  exceedingly  independent  official. 


1S8  BEET-SUGAR  MANUFACTURE. 

An  end  to   this  certainly  not  very  desirable  state  of  affairs   is 
brought  about  by  the  introduction  of  the  control  apparatus. 

Destruction  of  sugar  during  boiling  seems  practically  out  of  the 
question,  or  at  least  under  the  ordinary  conditions.  Since,  on 
account  of  the  previously  mentioned  grounds,  the  object  is  to  impart 
a  sufficient  motion  to  the  massecuite  in  the  boiling  apparatus  .and 
at  the  heating-surfaces  (and  as  a  matter  of  fact  this  can  be  accom- 
plished in  almost  every  case),  a  high  temperature  will  not  prevail 
throughout  the  most  of  the  mass  even  when  the  heating  is  in 
the  old-fashioned  way  with  direct  steam.  In  the  case  of  very 
tall  apparatus  there  may  be  a  loss  in  sugar  of  from  1-2  per  cent, 
when  such  are  not  provided  with  mechanical  stirrers,  and  in 
the  case  of  stiff  massecuites  it  is  possible  that  the  latter  may  be 
overheated  a  few  degrees  on  the  heating-surfaces.  But  even  in 
such  unfavorable  places,  which  as  a  matter  of  fact  are  only  met 
with  in  poorly  constructed  pans,  there  .can  be  no  very  great  over- 
heating above  85°  to  90°  (185°-194°  F.),  under  the  vacuum  of 
55  to  65  cm.  (21J  to  25J  in.)  which  ordinarily  prevails,  except  in 
those  cases  where  the  massecuite  is  burned  or  scorched  at  one  place. 
At  such  temperatures  it  is  impossible  that  there  should  be  a  percep- 
tible decomposition  of  sugar  in  an  alkaline  massecuite.  Even  when 
we  assume  that  portions  of  the  massecuite  have  temporarily  a  higher 
temperature  when  in  contact  with  the  heating-surfaces,  this  tempera- 
ture can  never  be  as  high  as  the  steam  used  for  heating,  and  the  latter 
has  a  maximum  temperature  of  from  115°  to  120°  C.  (239°  to  248°  F.), 
at  which  it  is  impossible  to  decompose  perceptible  amounts  of 
sugar.  Statements  to  the  contrary  which  have  sometimes  been 
recorded  can  be  true  only  under  extraordinary  conditions,  or  the 
experiments  were  made  with  inaccurate  methods  of  observation, 
so  that  they  are  lacking  in  proof.  It  must  be  remembered,  further- 
more, that  at  the  very  time  when  the  possibility  of  scorching  is  the 
greatest,  on  account  of  the  motion  of  the  mass  being  the  slightest, 
three-quarters  of  the  sugar  has  crystallized  out  and  will  then 
not  suffer  at  the  prevailing  temperature.  If  a  perceptible  amount 
of  sugar  is  decomposed  during  the  operation,  the  alkalinity  of  the 
sirup  must  increase  considerably,  for  there  will  be  0.4  of  a  part  of 


SUGAR-BOILING.  189 

potash  and  0.25  of  a  part  of  lime  set  free  for  each  part  of  sugar 
decomposed.  Such  an  increase  in  alkalinity  is,  however,  never 
met  with,  and  the  only  possible  indication  of  any  decomposition  is 
in  a  slight  decomposition  of  the  non-sugars  and  a  slight  amount 
of  ammonia  evolved.  If,  however,  the  sirup  boiled  is  neutral  or 
acid,  it  is  possible,  by  a  long-continued  boiling  and  by  high  tem- 
peratures of  the  masses  and  heating  vapor,  to  decompose  consider- 
able amounts  of  sugar. 

During  a  normal  boiling  there  are  no  mechanical  losses  of 
sugar.  Small,  fine  drops  are  never  formed  from  the  viscous  mass 
to  be  carried  off  mechanically  with  the  vapor;  as  the  bubbles 
of  steam  arise  and  break  on  the  surface  of  the  boiling  mass  large 
pieces  of  the  latter  are  loosened  and  thrown  up,  but  they  immediately 
sink  back  on  account  of  their  weight.  When  the  simp  is  thinner 
it  is  indeed  possible  for  tiny  drops  to  form ;  but  then  there  is 
greater  empty  space  above  the  liquid,  and  as  the  latter  becomes 
more  viscous  this  need  not  be  so  large.  There  should  always  be 
one  or  two  yards  of  empty  space  above  the  maximum  filling 
In  exceptional  cases  it  is  possible  that  there  pay  be  considerable 
foaming.  This  is  caused  sometimes  by  the  nature  of  the  juice,  or 
in  the  case  of  a  normal  juice  it  may  be  brought  about  by  suddenly 
increasing  the  vacuum,  when,  for  example,  the  condensers  are  not 
working  right  (owing  to  lack  of  water)  or  the  vacuum  is  increased 
at  the  air-pump.  The  massecuite  is  then  at  a  temperature  higher 
than  corresponds  to  the  boiling-point  of  the  greater  vacuum,  and 
the  excess  of  heat  is  suddenly  given  up  by  the  formation  of  a  large 
number  of  bubbles  of  steam.  In  such  cases  great  care  is  necessary 
to  prevent  some  of  the  massecuite  from  getting  into  the  vapor-pipes 
and  being  carried  to  the  condensers.  Diminishing  the  vacuum  by 
allowing  considerable  air  to  enter  by  closing  the  vapor-valve  and 
then  slowly  opening  it,  and  the  introduction  of  a  little  grease  until 
boiling  becomes  uniform  again,  are  the  means  employed  to  prevent 
foaming. 

Sugar-losses  may  be  caused  by  leaky  coils  or  heating-tubes,  and 
this  source  of  trouble  is  more  serious  here  than  in  the  multiple-effect 
evaporators,  because  in  such  cases  some  of  the  massecuite  may 


190  BEET-SUGAR  MANUFACTURE. 

enter  the  heating-space  or  get  into  the  condensed  water  with  each 
filling  of  the  apparatus.  On  this  account  it  is  desirable  to  test 
the  condensed  water  frequently  to  see  if  any  sugar  is  contained  in 
it,  and  particularly  when  the  apparatus  is  first  put  into  use. 

Larger  leaks  at  the  heating-surfaces  make  themselves  evident 
by  the  fact  that  some  of  the  condensed  water  enters  the  apparatus 
during  the  boiling,  whereby  the  formation  of  the  grain  and  in  fact 
the  whole  process  is  very  much  lengthened. 

One  of  the  worst  troubles  that  can  take  place  during  this 
part  of  the  process  is  the  so-called  "  heavy  boiling,"  which, 
according  to  the  degree,  may  be  made  manifest  by  a  lengthen- 
ing of  the  process  or  even  an  entire  cessation  of  the  boiling. 
This  is  met  with  in  working  up  juices  of  low  purity  made  from 
unripe  or  decayed  beets.  The  real  causes  have  never  been  entirely 
satisfactorily  explained.  Some  claim  that  the  difficulty  in  boiling- 
is  due  to  the  presence  of  lime  salts,  which  are  always  present  to 
some  extent,  while  others  believe  it  to  be  due  to  the  presence  of 
organic  constituents  which  are  present  in  large  quantities  compared 
to  the  amount  of  ash,  and  in  particular  those  substances  which 
result  from  the  pectic  substances  present  in  the  beets.  Both 
of  these  views  agree  in  so  far  as  there  are  always  large  amounts 
of  lime  salts  present  when  there  is  an  increase  in  the  organic 
matter  owing  to  the  poor  quality  of  the  beets. 

The  increase  in  the  amount  of  lime  salts  present  does  not, 
however,  of  itself  cause  the  difficult  boiling.  Such  lime  salts 
as  are  formed,  for  example,  by  the  decomposition  of  the  invert- 
sugar  and  nitrogenous  matter  by  caustic  lime,  do  not  exert  an 
injurious  effect  upon  the  boiling;  these  lime  salts  in  fact  are  not 
molasses-forming  to  the  extent  that  the  organic  potassium  salts 
are.  It  is  accordingly  clear  that  all  lime  salts  of  themselves  cannot 
be  looked  upon  as  the  cause  of  the  difficult  boiling,  and  any  conclu- 
sion with  regard  to  the  amount  of  lime  present  and  the  effect  upon 
the  boiling  is  likely  to  be  misleading. 

Difficult  boiling  is,  therefore,  caused  by  an  excess  of  lime 
salts  or  by  certain  non-saccharine  organic  matter.  These  in- 
jurious, organic  non-sugars  are  at  all  events  those  which  were 


SUGAR-BOILING.  191 

first  dissolved  during  the  diffusion  process  from  unripe  beets  or 
those  of  bad  quality.  The  amount  of  these  non-sugars  increases 
if  the  work  is  conducted  slowly  and  at  high  temperature.  Con- 
sequently, to  a  certain  extent  this  hard  boiling  may  be  avoided, 
or  at  least  the  difficulty  may  be  lessened,  if  the  diffusion  be  done 
quickly.  The  greatest  amount  of  these  non-sugars  is  dissolved 
naturally  in  the  sweetening  off  of  the  battery,  and  consequently 
the  last  boiling  of  the  week  will  show  this  phenomenon  of  hard 
boiling  to  the  greatest  extent. 

Sirups  which  are  insufficiently  saturated  with  carbonic-acid  gas 
are  always  boiled  down  with  difficulty;  for  this  reason,  also,  the  juices 
should  be  carefully  saturated.  Since  lime  sucrate  is  so  injurious 
upon  the  boiling  down,  it  seems  reasonable  to  assume  that  of  the 
different  lime  salts  only  those  can  cause  the  hard  boiling  which  are 
combined  with  organic  acids  of  high  molecular  weight,  and  it  is  to 
this  class  of  acids  which  the  pectic  substances  belong. 

As  a  preventive  of  hard  boiling,  disregarding  the  changing  of 
the  diffusion  work,  the  addition  of  soda  or  acid-sodium  sulphate 
has  been  recommended  in  order  to  effect  the  transformation  of  the 
lime  salts  into  the  corresponding  sodium  ones.  Even  if  this 
remedy  in  some  cases  does  not  prove  of  much  help,  yet  it  is  always 
advisable  to  try  it.  The  sodium  salts  are  added  to  the  thick  juice, 
or,  better  still,  to  the  thin  juice,  in  order  to  be  able  to  filter  off  the 
precipitated  carbonate  or  sulphate  of  lime.  It  is  not  necessary, 
however,  to  convert  the  entire  quantity  of  lime  salts  present  into 
sodium  salts,  but  it  suffices  to  add  from  one-quarter  to  one-half 
of  the  theoretical  amount,  for  apparently  the  injurious  lime  salts 
are  acted  upon  first.  In  fact  it  is  not  possible  to  decompose 
all  the  lime  salts  with  any  excess  of  soda. 

Another  remedy,  which  in  all  cases  accomplishes  good,  is  the 
artificial  movement  of  the  mass  in  the  boiling-apparatus,  and 
particularly  stirring  that  is  brought  about  by  introduction  of 
steam  which  enters  at  the  bottom  of  the  apparatus  through  a 
sp raving-arrangement.  In  this  way  an}'  amount  of  bubbles  of 
steam  may  be  introduced  and  driven  through  the  mass,  thus  giv- 
ing it  a  uniform  motion,  so  that  finally  the  heat-transference  and  the 
crystallization  take  place  satisfactorily. 


192  BEET-SUGAR   MANUFACTURE. 

When  the  hard  boiling  occurs,  then,  owing  to  the  viscosity  of 
the  mass  and  the  irregular  heat-transference,  there  is  usually  a 
violent  foaming.  In  this  case  also,  the  introduction  of  live  steam 
neutralizes  the  cause  of  the  foaming  and  is  the  best  remedy;  it 
should  be  tried  in  all  cases  before  resorting  to  the  use  of  grease  or  oil. 

By  improper  handling  of  the  pan  it  is  possible  in  some  forms  of 
apparatus  that  another  difficulty  may  be  met  with,  and  that  is  the 
formation  of  hard  lumps  in  the  massecuite.  These  lumps  are  formed 
chiefly  at  the  beginning  of  the  boiling  and  in  those  forms  of  apparatus 
where  the  heating-surfaces  are  not  entirely  covered  with  juice  at 
this  stage.  The  concentrated  juice  then  spatters  against  the  upper 
portion  of  the  heating-surfaces  (steam-coils),  the  drops  adhere 
firmly  and  sugar  crystallizes  out,  remaining  together  with  the  sirup 
adhering  to  the  heating-surface,  and  particularly  when  these  coils 
retain  steam  on  account  of  the  valves  not  being  perfectly  tight. 
The  spattered  lump  adheres  so  firmly  at  some  places  that  it  cannot 
be  loosened  even  although  it  may  subsequently  rest  in  the  centre 
of  the  boiling  massecuite.  Naturally  the  adhering  mass  cannot  be 
dissolved  off,  as  it  is  constantly  surrounded  by  supersaturated 
juices,  and  if  steam  is  then  gradually  introduced  into  the  upper 
heating-surfaces  it  burns  fast  to  the  steam-coil,  forming  hard  scale, 
fragments  of  which  of  considerable  size  may  be  found  at  the  corners 
of  the  coil-hangers,  or  at  the  flanges.  This  scale  shows  a  crystalline 
cleavage.  By  reason  of  the  changes  in  temperature,  and  partic- 
ularly as  the  heating-surfaces  first  warm  up,  the  pieces  crack  off 
and  mix  with  the  massecuite  and  the  sugar,  of  which  only  the 
larger  fragments  are  purged  out.  Hard  lumps  can  also  form  in 
the  lower  parts  of  the  pan  when  the  coils  are  placed  so  closely 
that  they  prevent  movement  of  the  massecuite  and  allow  it  to 
burn  on  to  the  steam-coils. 

The  fact  that  the  massecuite  contains  such  lumps  and  scales 
is  recognized  at  the  time,  as  they  have  the  shape  of  the  coils 
or  tubes  inside  the  apparatus.  Those  scales  that  are  formed  in 
the  upper  part  usually  show  a  finely  crystalline  nature,  while  those 
lower  down,  which  have  been  formed  between  the  coils  during  thick- 
ening of  the  massecuite,  show  a  more  coarsely  crystalline  structure. 


SUGAR-BOILING.  193 

This  formation  of  scales  is  naturally  best  avoided  by  using  a 
vacuum-pan  with  properly  built  heating-surfaces.  In  those  forms 
of  apparatus  with  vertical  tubes,  which  from  the  very -beginning 
are  covered  writh  juice,  they  are  never  formed.  In  apparatus 
having  coils  and  similar  heating-arrangements  they  are  formed  to 
a  greater  or  less  extent;  it  is  then  necessary  to  take  care  that  they 
do  not  reach  the  sugar.  To  prevent  this,  all  deposits  upon  the 
coils  must  be  dissolved  off  after  removal  of  the  massecuite  at  the 
end  of  each  boiling  and  before  the  introduction  of  a  new  lot  of  juice. 
It  is  not  advisable  to  attempt  to  dissolve  these  deposits  by  means 
of  the  sirup  itself,  for  as  a  rule  the  latter  is  concentrated  so  rapidly 
that  it  has  little  if  any  solvent  action.  The  apparatus  should  be 
steamed  out  until  it  is  absolutely  certain  that  every  bit  of  deposit 
upon  the  coils  has  been  removed.  This  is  best  accomplished  by 
placing  perforated  steam-pipes  over  those  places  where  the  deposits 
are  likely  to  form,  in  such  a  way  that  the  steam  will  be  directed 
inward  them.  Frequently  this  treatment  results  in  some  of  the 
scales  being  broken  off  by  expansion;  in  such  cases  it  is  advisable 
to  separate  the  steaming  water  containing  Jhese  sugar  residuals 
and  send  it  to  the  sirup,  or  allow  it  to  run  through  a  strainer  to 
remove  the  lumps. 

The  introduction  of  direct  steam  during  boiling  acts  very 
advantageously  in  preventing  the  formation  of  these  lumps  and 
scales  in  the  lower  part  of  the  apparatus.  But  even  then,  in  case 
the  vacuum-pan  is  of  too  close  construction  with  coils  or  tubes 
packed  together,  it  is  necessary  to  thoroughly  steam  out  after  each 
boiling,  and  this  is  best  done  by  letting  in  steam  from  beneath  as 
well  as  from  above  and  through  the  coils. 

In  other  respects,  also,  a  good  steaming  out  is  advantageous  at 
the  completion  of  each  boiling.  In  all  cases  a  little  of  the  masse- 
cuite is  certain  to  remain  adhering  to  the  more  prominent  parts 
of  the  apparatus  and  the  crystals  are  only  partially  dissolved,  if 
at  all,  in  the  sirup  which  is  next  treated;  in  case  the  juice  is  already 
strongly  concentrated,  there  will  be  a  certain  amount  of  coarser 
crystals  in  the  presence  of  the  newly  formed  and  finer  ones,  and 
the  presence  of  the  former  is  by  no  means  desirable.  By  steaming 


194  BEET-SUGAR  MANUFACTURE. 

out  the  pan,  all  of  the  massecuite  remaining  in  the  apparatus  is 
either  made  to  flow  out  of  the  pan,  or  if  it  remains,  it  is  in  a  dis- 
solved condition. 

It  is  particularly  desirable  to  arrange  to  have  that  part  of 
the  pan  in  the  vicinity  of  the  sight-glasses  well  steamed  out,  for 
these  glasses  always  have  a  little  offset,  which  makes  a  hollow  on 
the  inside  that  is  particularly  likely  to  be  filled  with  massecuite, 
and  unless  the  apparatus  is  provided  with  an  especial  arrangement, 
this  is  likely  to  retain  undissolved  sugar  both  from  the  steaming-out 
process  and  from  the  next  change  of  sirup.  Clean  sight-glasses 
are  especially  necessary  for  the  work,  so  that  it  is  well  to  blow  a 
fine  stream  of  water-vapor  against  them  after  each  boiling  until 
they  are  perfectly  clean.  When  the  holes  in  the  steam-pipe  are 
made  so  small  that  the  steam  escapes  in  a  very  fine  spray,  there 
is  no  danger  of  breaking  the  glass. 

The  diluted  massecuite  which  flows  from  the  apparatus  during 
the  steaming-out  process,  and  which  if  the  process  is  continued  for 
some  length  of  time  eventually  forms  a  thin  sirup,  is  in  the  case  of 
tank-work  emptied  into  a  separate  tank;  when  crystallizers  are  used 
it  serves  for  the  dilution  of  the  massecuite,  which  is  usually  obtained 
in  a  too  viscous  condition.  It  does  not  seem  always  necessary  to 
collect  separately  the  juice  obtained  in  the  steaming-out  process, 
because  when  the  mother-liquor  is  diluted  by  it  the  supersaturation- 
coefficient  is  still  as  high  as  is  necessary  for  satisfactory  completion  of 
the  process. 

With  regard  to  variations  in  the  customary  methods  of  con- 
ducting the  boiling-in-grain  process,  there  are  practically  none,  if 
we  disregard  individual  tricks  of  the  sugar-boilers  which  are  usually 
not  essentially  different  and  often  apply  only  to  the  particular 
factory  in  question.  Perhaps  it  might  be  mentioned  in  this  con- 
nection that,  to  obtain  extra-large  crystals,  the  practice  is  to  divide 
the  finished  strike  of  one  pan  between  two  pans  j  ust  before  the  in- 
troduction of  the  last  portion  of  sirup,  and  work  up  the  two 
halves  separately,  or  let  half  run  out  of  the  pan  and  continue 
the  boiling  of  the  rest  till  the  pan  is  full.* 

In  some  factories  it  is  considered  best  to  make  but  one  raw- 
*  This  is  known  as  making  a  "cut." — TRANSLATORS. 


SUGAR-BOILING.  195 

sugar  product  (firsts  or  granulated)  and  the  molasses.  In  such 
cases  it  is  not  permissible  to  mix  any  sugar  that  subsequently 
crystallizes  out^with  the  first  product,  as  is  sometimes  done  in 
certain  countries  to  the  detriment  of  the  quality  of  the  product 
manufactured.  It  is  desirable  in  these  factories  always  to  begin 
the  boiling  process  with  sirup  and  later  on,  by  the  addition  of 
sirup  and  long-continued  boiling,  to  carry  the. work  so  far  that 
in  the  crystallizers  all  of  the  sugar  possible  is  obtained,  with  the 
mother-sirup  entirely  converted  into  molasses. 

The  usual  method  is  to  conduct  a  few  boilings  at  the  start  in  the 
customary  manner.  When  enough  of  the  sirup  that  drains  off  has 
been  collected,  the  sirup  is  boiled  down  to  a  finely  granular  masse- 
cuite  and  in  such  a  way  that  the  pan  is  approximately  half-filled, 
then  sirup  is  introduced  and  the  boiling  is  continued  by  the  method 
which  will  be  described  later  on  for  the  boiling  of  " after-product" 
sirup  to  grain.  Such  a  boiling  should  require  at  least  20  to  24 
hours,  while  at  least  4  days  are  necessary  for  the  work  in  the 
crystallizers  if  an  actual  molasses  is  to  be  obtained.  The  masse- 
cuite  obtained  in  such  a  way  is  as  coarsely  ^granular  as  a  normal 
Xo.  1  product,  and  the  sugar-yield  is  equally  good,  so  that  in  these 
respects  it  is  just  as  good  a  product  as  that  obtained  from  the 
previous  boilings.  With  regard  to  the  refining  of  the  product 
however,  there  is  this  difference :  it  is  not  possible  to  obtain  white 
crystals  after  centrifugation.  If  such  a  sugar  be  mixed  with  the 
product  obtained  in  the  usual  way,  and  if,  as  is  the  case,  the  dark- 
colored  product  is  not  valued  as  highly,  it  appears  very  doubtful 
as  to  whether  it  is  advisable  to  work  in  this  manner.  It  is  a  ques- 
tion to  be  determined  only  by  a  careful  calculation  in  which  all 
the  different  factors  are  taken  into  consideration. 

In  order  to  conduct  the  boiling  operation  according  to  this 
last-mentioned  plan  it  is  necessary  that  the  sugar-boiler  should  be 
very  skillful  and  absolutely  trustworthy.  In  order  to  obtain 
perfectly  uniform  results  it  is  necessary  to  make  use  of  a  boiling- 
control  apparatus  provided  with  the  necessary  scales. 


CHAPTER  XVI. 
WORKING  UP  THE  "MASSECUITE." 

IN  emptying  the  massecuite  into  coolers  or  an  ordinary  mixer, 
a  regulated  crystallization  of  the  sugar  is  out  of  the  question.  The 
only  precaution  to  be  taken  is  to  prevent  too  rapid  cooling.  As 
has  already  been  mentioned,  the  sugar  now  crystallizes  to  some 
extent  upon  the  large  crystals  already  formed,  but  also  upon 
crystals  formed  during  the  boiling,  discharging,  or  cooling,  and 
which  are  so  small  that  only  a  small  portion  of  them  can  be  re- 
covered in  their  present  size.  The  chief  object  of  the  process, 
namely,  an  increase  in  sugar-yield,  cannot  be  accomplished  by 
tank-work  or  by  mixers.  At  this  stage  the  only  aim  is  to  bring 
the  mass  to  such  a  condition  that  it  is  suitable  for  centrifugal 
purging. 

In  the  cooler  (tank)  process,  the  sugar  is  expelled  from  the 
coolers  by  compressed  air  in  the  form  of  blocks  of  massecuite 
which  are  more  or  less  hard  and  brittle  according  to  the  method 
of  boiling  and  the  rate  of  cooling  the  massecuite.  It  is  broken 
up  in  the  small  mixers  and  mashed  with  more  or  less  sirup.  Ac- 
cording to  the  extent  of  the  cooling  that  the  mass  has  under- 
gone, hot  or  cold,  thick  or  thin  sirup  is  used  for  this  purpose. 
If  a  large  number  of  mealy  crystals  have  been  formed  so  that 
it  will  be  hard  to  centrifugate  the  mass,  it  is  necessary  to  add  suf- 
ficient hot  sirup  to  redissolve  these  fine  crystals.  There  is  in 
fact  no  better  criterion  for  regulating  the  amount  of  sirup  added 
to  the  massacuite  than  the  ease  of  working  in  the  centrifugals. 
Usually  the  workman  is  paid  "by  the  piece/'  and  it  is  on  this 
account  that  the  general  tendency  is  to  add  too  much,  too  thin, 
or  too  hot  sirup. 

196 


WORKING  UP  THi:    "MASSECUITE."  197 

In  the  ordinary  mcthml  of  hot  purging  there  cannot  be  a 
proper  regulation  of  the  temperature,  although  this  is  the  chief 
requisite  for  good  crystallization.  The  favorable  temperature 
for  eentrifugation  is  from  40°  to  50°  C.  (104°  to  122°  F.),  and  the 
nuissecuite  is  brought  to  this  temperature  as  quickly  as  possible  by 
a<  Iding  water  or  dilute  sirup  until  it  is  sufficiently  mobile.  Working 
in  mixers  has  the  advantage  over  cooling-tanks  that  it  permits 
cleaner  work  in  the  sugar-house.  On  the  other  hand,  the  yield 
by  the  other  method  is  greater  and  the  quality  of  the  product 
poorer.  By  either  method  of  working,  however,  the  molasses 
seldom  has  a  purity  less  than  78  to  80  per  cent. 

Rational  working  up  of  massecuite  can  only  be  carried  out 
when  this  has  been  properly  boiled  with  sirup  and  when  the  tem- 
perature and  concentrations  have  been  systematically  regulated. 
The  sugar-yield  from  the  massecuite  can  only  be  increased  to  a 
certain  extent,  and  this  increase  is  in  proportion  to  the  diminution 
in  purity  of  the  sirup  which  drains  off  from  it. 

The  working  up  of  the  massecuite  depends  upon  the  principle 
that  from  every  sirup  which  has  not  been  too  strongly  concentrated 
the  sugar  crystallizes  out  satisfactorily  only  when  there  are  a 
sufficient  number  of  exciting  crystals  present,  and,  furthermore. 
upon  the  fact  that  a  solution  of  sugar  which  is  saturated  or  slightly 
supersaturated  at  a  high  temperature  becomes*  strongly  super- 
saturated upon  cooling.  The  aim  is,  therefore,  to  conduct  the 
cooling  hi  such  a  way  that  the  supersaturation  coefficient  of  the 
mother-sirup  under  no  conditions  exceeds  the  limit  above  which 
there  is  a  tendency  to  form  new  crystals,  while  on  the  other  hand 
the  cooling  should  take  place  rapidly  enough  so  that  the  coefficient 
remains  at  least  1.05-1.10;  because  if  the  extent  of  supersaturation 
is  slight  the  crystallization  takes  place  altogether  too  slowly. 
Crystallization  takes  place  to  some  extent  of  its  own  accord  after 
the  massecuite  has  been  discharged  from  the  vacuum- pan,  because 
the  massecuite  is  filled  with  more  or  less  strongly  supersaturated 
mother-sump  and  is  only  brought  about  by  cooling  which  increases 
the  low  supersaturation-coefficient  till  the  original  value  is  prac- 
tically attained.  The  chief  requirement  for  the  whole  work  is 


198  BEET-SUGAR   MANUFACTURE. 

that  the  entire  massecuite  should  be  maintained  at  a  uniform 
temperature  and  concentration,  or  in  other  words  that  the  mass 
be  sufficiently  agitated. 

The  prevailing  idea  in  the  use  of  stirrers  and  other  appliances 
in  "  crystallization  in  motion  "  is  that  this  stirring  is  a  direct 
cause  of  crystal  formation.  This  view  is  entirely  wrong.  The 
sugar  particles  directly  in  contact  with  a  sugar  crystal  are  the 
only  ones  which  enter  in  its  growth.  When  this  film  becomes 
exhausted,  and  hence  less  concentrated,  a  diffusion  begins  be- 
tween this  and  the  adjacent  sirup  film. 

The  more  favorable  the  conditions  for  this  diffusion  the  more 
rapidly  crystallization  goes  on.  Since  the  greatest  impediment 
to  diffusion  is  viscosity,  any  conditions  which  lessen  viscosity 
hasten  crystallization.  The  viscosity  increases  greatly  in  propor- 
tion to  the  extent  of  supersaturation  and  to  the  drop  in  temper- 
ature. Hence  the  use  of  a  moderate  supersaturation  and  proper 
temperature  is  of  the  utmost  importance  for  good  crystallization. 

Stirring  has  no  effect  on  any  of  these  conditions.  It  does 
bring  about  equal  temperature  conditions  and  in  large  degree  an 
equal  density  throughout  the  massecuite.  This  action  is  also  of 
great  importance  because  it  hinders  the  formation  of  second 
grain  and  keeps  the  grain  already  formed  equally  distributed 
through  the  massecuite.  Therefore,  stirring  only  partially  aids 
crystallization,  which  is  entirely  dependent  on  a  diffusion  action. 

To  accomplish  this  in  working  up  massecuite  crystallizers  are 
used.  They  usually  consist  of  horizontally  placed,  closed,  cylin- 
drical retainers  which  are  provided  with  a  double  mantle  or  other 
arrangement  for  heating  or  cooling  the  contents,  and  a  suitable 
stirring-arrangement  inside,  or  they  themselves  revolve  upon  an 
axis.  The  massecuite  is  transferred  from  the  boiling-pan  to  the 
crystallizer  by  gutters  in  case  the  former  is  above  the  latter; 
otherwise  the  massecuite  is  removed  from  the  vacuum-pan  by 
compressed  air  and  forced  up  to  the  crystallizer,  or  by  means  of  a 
vacuum  in  the  latter  is  sucked  up  into  it.  It  is  not  recommended 
to  pump  up  first  product  on  account  of  too  great  cooling  in  the 
pipes  or  foaming. 


WORKING   UP  THE  "  MASSECUITE."  199 

There  are  two  methods  of  using  crystallizers.  By  the  first  method 
the  massecuite  is  filled  with  fairly  strongly  supersaturated  mother- 
sirup,  so  that  the  supersaturation-coefficient  is  about  1.3.  Such  a 
mass  contains  from  6  to  7  per  cent  of  water  and  should  not  be 
cooled  much  at  first,  but  it  must  be  kept  at  the  original  temperature 
of  75°  to  80°  C.  (167°  to  176°  F.)  for  several  hours;  the  reason  for 
this  is  that  the  supersaturation  is  so  great  that  new  crystals  would 
immediately  form  if  the  massecuite  were  cooled.  When  the 
crystallization  has  proceeded  to  the  point  when  the  supersaturation 
coefficient  is  reduced  to  1.1  to  1.2,  the  mass  is  slowly  allowed  to 
cool.  If  at  the  end  of  from  18  to  24  hours  the  temperature  has 
been  lowered  to  about  60°  C.  (140°  F.),  enough  thin  dilute  sirup 
must  be  added  to  render  the  mass  sufficiently  fluid  so  that  it  can 
be  centrifugated.  The  work  in  the  crystallizer  is  complete  when 
the  temperature  has  been  reduced  to  55°  C.  (131°  F.). 

Since  there  is  more  danger  of  making  mistakes  when  the  attempt 
is  made  to  work  with  stiff  massecuites,  it  is  usually  preferable 
to  work  with  thin  ones.  Of  course  it  is  possible  to  boil  such  a 
massecuite  until  it  has  a  supersaturation-coefficient  of  1.3,  and  this 
is  always  advisable.  After  discharging  the  vacuum-pan  the  con- 
densed water  from  steaming  out  is  allowed  to  run  upon  the  masse- 
cuite  in  the  crystallizer,  or  a  little  dilute  sirup  is  added  so  that 
the  supersaturation-coefficient  of  the  mother-liquor  sinks  to  about 
1.15  to  1.2.  Such  a  mass  contains  from  8  to  8^  per  cent  of  water 
and  can  be  cooled  at  once  and  relatively  rapidly.  At  the  end 
of  15  to  20  hours  it  may  reach  the  temperature  of  from  45° 
to  55°  C.  (113°  to  131°  F.)  without  the  formation  of  any  new 
crystals  or  necessity  of  further  dilution. 

Naturally  it  is  not  possible  to  obtain  as  great  sugar-yield  in 
the  last-mentioned  case  as  when  undiluted  and  stiff-cooked  masse- 
cuite is  worked  up.  In  working  up  these  lighter  massecuites, 
ordinarily  the  sirup  that  drains  off  has  a  purity  of  but  75  per  cent, 
and  the  purity  is  less  only  when  the  boiling  with  sirup  is  long- 
continued;  in  the  case  of  undiluted  masaecuites,  on  the  other  hand, 
it  is  possible  to  reduce  the  sugar  in  the  sirup  to  less  than  70  per 
cent.  To  be  sure,  this  requires  greater  attention,  and  in  case  the 


200  BEET-SUGAR  MANUFACTURE. 

proper  attention  is  not  paid,  massecuites  are  obtained  which  are 
very  hard  to  centrifugate ;  this  difficulty  is  then  only  overcome 
by  heating  and  diluting,  and  during  this  process  so  much  sugar 
is  dissolved  out  that  the  yield  is  greatly  lessened. 

A  method  of  working  up  massecuites  which  on  its  face  appears 
quite  different  is,  in  principle,  essentially  the  same,  and  that  is 
the  working  up  in  the  so-called  "  Kochmaischen."  These  are  air- 
tight crystallizers  into  which  the  mass  after  being  boiled  down 
in  .the  pans  can  be  transferred  under  vacuum  very  slowly  and  with 
the  proper  addition  of  dilute  sirup  can  be  boiled  further  and  finally 
allowed  to  cool  off.  This  apparatus,  therefore,  acts  at  the  begin- 
ning as  a  vacuum-pan,  with  very  small  heating-surfaces,  and  later 
as  a  crystallizer. 

When  such  an  apparatus  is  used,  the  crystallization  of  the 
sugar  is  brought  about  at  first  merely  by  means  of  a  slow  evap- 
oration, and  only  towards  the  end  by  cooling.  Theoretically,  the 
evaporation  should  take  place  so  that  the  supersaturation  coeffi- 
cient of  from  1.2  to  1.3  is  always  maintained,  and  if  it  were  possible 
to  accomplish  this  in  practice,  there  is  no  doubt  but  that  this 
method  would  furnish  a  most  rapid  crystallization  and  would  be 
preferred  to  the  use  of  crystallizers.  As  a  matter  of  fact,  however, 
there  is  no  way  of  determining  whether  the  proper  supersaturation 
prevails.  In  almost  every  case  new  crystals  are  formed  which 
must  be  afterwards  redissolved  by  thin  sirup  and  in  this  way, 
naturally,  the  whole  continuity  of  the  process  is  disturbed.  Conse- 
quently it  cannot  be  said  that  better  results  or  quicker  working 
are  obtained  with  this  form  of  apparatus. 

No  matter  which  method  of  working  up  massecuite  is  used, 
crystallization  never  takes  place  as  rapidly  as  in  the  vacuum-pan, 
because  the  mother-sirup  already  has  a  lower  purity  and  this  con- 
stantly becomes  less.  It  does  not  seem  advantageous,  in  the 
case  of  normal  working,  to  carry  the  crystallization  of  the  sugar 
from  the  mother-sirups  too  far  in  the  manufacture  of  first  product. 
This  would  require  too  many  vacuum-pans  with  stirring  arrange- 
ments and  of  crystallizers  or  "  Kochmaischen."  Usually  it  is 
considered  satisfactory  to  stop  when  the  sirup  that  runs  off  con- 


woRKixr,  UP  THI:  -  MASSECUITE."  201 

tains  75  per  cent  of  sugar;  only  a  few  factories  attempt  to  reduce 
the  purity  to  70  or  72,  while  a  great  many  stop  when  the  sirup 
contains  more  than  75  per  cent  of  sugar.  For  making  good  raw 
sugar  which  leaves  the  centrifugals  perfectly  white  and  can  be  easily 
refined,  the  purity  of  the  sirup  should  not  be  lowered  too  much. 

Indeed,  the  purity  of  the  sirup  that  drains  off  depends  not 
only  upon  the  method  of  working  and  upon  the  duration  of  the 
crystallization  process,  but  also,  not  inconsiderably,  upon  the 
amount  and  size  of  the  crystals  present.  The  finer  the  crystals 
are,  the  more  exciting  faces  are  present  to  hasten  the  crystallizing 
of  the  sugar  and  consequently  the  more  rapid  is  the  crystalliza- 
tion. Whereas  one  kilogram  of  very  coarse  granular  raw  sugar 
presents  a  total  outer  surface  of  crystals  amounting  to  about  3  square 
meters,  the  same  weight  of  fine  crystals  may  have  a  surface  of 
about  7  square  meters.  If  it  be  desired  simply  to  obtain  a  speedy 
crystallization  of  the  sugar,  without  paying  any  attention  to  any 
other  particular,  the  aim  should  be  to  form  a  large  number  of 
fine  crystals.  The  preparation  of  a  coarsely  granular  sugar  with 
a  correspondingly  equal  desugarizing  of  the  mother-sirup  always 
requires  relatively  more  time,  and  consequently  more  space  to  be 
taken  up  by  vacuum-pans  and  crystallizers. 


CHAPTER  XVII. 
THE    CENTRIFUGAL  WORK. 

IF  the  massecuite  of  the  first  product  has  been  properly 
boiled  down,  the  separation  of  the  sirup  from  the  sugar  crystals 
in  the  centrifugal  machines  presents  no  difficulties;  this  part  of  the 
work  then  becomes  the  simplest  operation  in  the  whole  process. 

The  centrifugals  themselves  are  either  suspended  or  standing. 
In  Germany  the  latter  type  is  used  almost  exclusively,  although  in 
certain  respects  the  former  has  advantages.  Whereas  formerly  the 
drums  of  the  centrifugals  always  had  a  diameter  of  about  800  milli- 
meters (30  inches)  and  for  one  filling  in  the  neighborhood  of  SO  to 
100  kilos  of  massecuite  was  sufficient  (175  tc  220  Ibs.),  at  the  present 
time  centrifugals  of  much  greater  diameter,  with  a  capacity  of 
150  to  500  kilos  (330  to  1100  Ibs.)  and  arranged  for  discharging  at 
the  bottom,  are  in  use.  In  this  way  a  great  deal  of  labor  is  saved. 
Experiments  in  the  attempt  to  make  a  continuous  centrifugal 
have  miscarried. 

For  the  best  centrifugal  work  some  attention  must  be  paid  to 
the  holes  of  the  strainer.  To  prevent  the  strainer  from  lying  flat 
against  the  walls  of  the  drum,  thereby  making  a  large  part  of  the 
holes  or  slits  inactive,  there  must  be  placed  under  each  strainer 
another  wide-meshed  sieve,  thus  giving  the  necessary  interspace 
between  the  strainer  and  the  sides  of  the  drum.  The  holes  or 
slits  must  be  made  as  fine  as  possible,  small  but  not  so  small  that 
they  are  stopped  up  by  the  crystals.  The  suitable  size  must  be 
determined  by  experiment  in  each  separate  factory.  There  does 
not  seem  to  be  any  special  advantage  in  having  these  holes  or 
slits  of  conical  shape,  and  this  is  also  true  with  regard  to  many 

other  of  the  so-called  improvements;    the  chief  requisite  is  the 

202 


THi:  CKXTHIITGAL  WORK.  203 

shape  and  size  of  the  holes  on  the  inside.  Smooth  strainers  made 
of  sheet  metal  are  usually  preferred  to  those  made  of  cloth. 

The  introduction  of  the  massecuite  into  the  centrifugals,  when 
the  mixers  or  crystallizers  are  above  them,  is  effected  by  means 
of  spouts  or  wagons;  if  the  mixers  are  at  the  same  level  or  lower, 
the  massecuite  is  first  carried  from  the  crystallizer,  which  is  made 
air-tight,  either  by  means  of  compressed  air,  or  by  peculiarly  con- 
structed pumps,  into  an  intermediate  mixer  at  a  higher  level, 
whence  it  runs  by  gutters  or  spouts  to  the  centrifugals  below. 

The  wagons  have  the  advantage  that  the  massecuite  is  cooled 
but  little  and  that  each  centrifugal  can  be  filled  with  an  accurately 
measured  amount  of  massecuite,  although  the  work  is  not  so  clean 
as  is  the  case  when  spouts  are  used,  each  of  which  is  provided  with  a 
discharge-gate  above  the  centrifugal.  Even  stiff  massecuites  will 
flow  sufficiently  well  in  such  spouts,  although  it  is  very  practical 
to  place  a  shaft  with  short  stirring-arms  in  such  a  way  that  the 
mass  is  slowly  and  steadily  stirred,  thus  preventing  a  deposition 
of  sugar  crystals  upon  the  bottom.  It  is  also  very  advisable  to 
provide  the  mixer  with  a  steam-jacket,  although  it  is  rarely  neces- 
sary to  heat  the  massecuite  in  the  mixers  during  the  normal  process 
of  manufacture  of  "  firsts,"  but  it  is  sometimes  desirable  in  the 
case  of  massecuites  which  do  not  work  well  in  the  machines,  when 
it  is  necessary  to  keep  them  in  the  gutters  for  some  time.  If  the 
centrifugals  are  filled  when  not  in  motion,  as  is  usually  the  case 
with  "firsts,"  it  is  feasible  to  use  an  indicator  on  the  inner  cone 
of  the  machine  to  determine  when  the  centrifugal  has  been  properly 
charged.  The  operator  is  usually  able  to  judge  the  proper  amount 
very  accurately  with  his  eye,  even  when  the  centrifugal  is  in 
motion,  as  is  frequently  the  case  in  working  up  "  seconds."  When 
the  massecuites  are  easily  cent rifuga ted  the  sirup  is  removed  from 
the  crystals  before  the  machine  has  attained  the  normal  number 
of  revolutions  per  second.  Naturally,  crystals  lying  directly 
against  the  strainer  retain  less  sirup  than  those  in  the  interior,  but 
this  difference  is  very  slight,  and  during  discharging  of  the  cen- 
trifugals and  the  transportation  of  the  sugar-product  the  latter 
usually  becomes  uniformly  mixed. 


204  BEET-SUGAR   MANUFACTURE. 

When  the  centrifugal  work  becomes  difficult  it  is  necessary  to 
drive  the  machines  for  a  considerable  length  of  time  at  their  maxi- 
mum velocity.  In  such  cases  some  portions  of  the  contents  are 
even  then  found  to  be  badly  purged.  It  is  extremely  hard  to  remedy 
this  while  the  massecuite  is  in  the  centrifugal,  or  at  any  event 
without  incurring  considerable  sugar-losses,  and  it  is  far  better 
to  aim  at  preventing,  rather  than  remedying,  the  trouble.  The 
difficulty  is  usually  caused  by  the  presence  of  a  fine  crystal  meal, 
which  is  formed  in  more  or  less  quantity  by  a  crystallization  process 
improperly  conducted. 

There  are,  to  be  sure,  certain  other  causes  of  difficult  or  very 
slow  centrifugal  work,  such  as  foamy  stirring  and  the  massecuite 
cooling  and  graining  out  too  much. 

The  massecuite  can  be  stirred  until  it  becones  filled  with  foam, 
both  in  the  crystallizers  and  in  the  mixers,  if  the  arms  or  wings 
of  the  stirrer  project  in  such  a  way  that  air  is  stirred  into  the 
sugar  mass.  To  prevent  this  the  stirring  arrangement  should  be 
entirely  covered  with  the  sugar.  When  emptying  a  crystallizer 
the  stirring-arms  will,  however,  reach  out  into  the  air,  but  it 
is  not  advisable  to  stop  the  stirring,  because  in  that  case  crystals 
will  settle  out  on  the  bottom,  and  it  will  then  be  impossible  to 
start  stirring  again;  it  is,  therefore,  better  to  stir  very  slowly 
at  this  point,  so  that  an  appreciable  amount  of  foam  will  not  be 
formed.  If  the  stirrer  then  makes  one-half  to  one,  or  at  most 
one  and  one-half  revolutions  per  minute,  it  is  sufficient  to  main- 
tain a  uniform  temperature  throughout  the  mass.  It  is  easy  to 
understand  without  explanation  why  the  foamy  masses  are  difficult 
to  centrifugate  properly,  because  the  lighter  and  foamy  sirup 
deposits  upon  the  crystals,  forming  a  tough  film  which  cannot  be 
forced  through  the  sugar  by  means  of  the  centrifugal  force. 

It  is  also  advisable  to  avoid  cooling  the  massecuite  too  far. 
The  point  of  effective  cooling  must  be  regulat3cl  first  of  all, 
according  to  the  extent  of  supersaturation,  which  in  good  work 
is  always  small;  it  is  dependent  chi^iiy,  however,  on  the  amount 
that  the  mother-sirup  is  desugarized,  -i.e.,  its  purity.  The  less 
this  is,  the  higher  the  purging  temperature  will  have  to  be,  since 


THE  CENTRIFUGAL  WORK.  205 

the  viscosity  of  a  sirup  of  low  purity  increases  much  faster  as  the 
temperature  drops  than  in  a  sirup  of  higher  purity  having  an 
equal  supersaturation. 

Massecuites  having  a  sirup  of  high  purity  can  be  cooled  to 
40-45°  (104-113°  F.),  but  those  having  a  much  desugarized  sirup 
will  purge  better  at  50-60°  (122-140°  F.).  Cooling  while  on  -the 
way  from  crystallizers  to  centrifugals  is  always  bad,  and  should 
be  provided  against  by  suitable  contrivances. 

However,  it  is  only  in  the  case  of  excessively  cooled  massecuites 
that  the  viscosity  is  the  cause  of  the  bad  working  or  prolong- 
ing the  time  required  in  centrifugation.  In  the  case  of  warm 
massecuites  it  plays  no  part  at  all,  except  when  a  finely  crystalline 
meal  is  present.  This  crystal  meal  separates  out  upon  the  larger 
crystals  as  in  the  case  of  the  foamy  sirup  through  the  action 
of  centrifugal  force.  When  the  centrifugals  act  badly  there 
usually  rests  upon  the  strainer  a  layer  of  sugar  which  has  been 
more  or  less  satisfactorily  drained  of  its  sirup,  then  follows  a 
tough  layer  of  tiny  crystals  cemented  together,  and,  finally,  there 
is  more  or  less  of  the  sirup  which  has  been  unable  to  penetrate 
this  layer. 

If  such  massecuite  has  been  made  by  improper  boiling  there  is 
nothing  else  to  do  but  dissolve  the  meal  in  the  crystallizers  or 
mixers  by  the  addition  of  very  hot  or  very  dilute  sirup.  If  this  is 
done  very  carefully  there  is  little  danger  of  dissolving  out  any  great 
amount  of  sugar  from  the  larger  crystals.  In  working  with  crystal- 
lizers it  is,  furthermore,  always  possible  to  regain  the  greater  amount 
of  the  dissolved  sugar  by  a  properly  conducted  cooling  process. 

The  suitability  of  the  massecuite  for  centrifugation  depends  on 
the  amount  of  this  crystalline  meal  and  its  fineness.  A  little 
of  this  meal  or  fine  crystals  is  present  in  every  case,  as  can  be 
easily  proven  by  the  microscope.  If  it  be  found  that  the  masse- 
cuite is  unsuitable  for  centrifugal  work  after  it  has  been  intro- 
duced into  the  machines  there  is  nothing  to  do  but  introduce 
steam  during  the  purging  which  redissolves  the  finer  crystals  and 
heats  the  sirup.  It  is  preferable  to  introduce  steam  between  the 
drum  and  the  mantle  rather  than  from  inside  the  drum,  because 


206  BEET-SUGAR  MANUFACTURE. 

in  the  latter  case  the  steam  acts  more  slowly  and  uniformly,  so 
that  much  sugar  is  not  dissolved  off  from  the  large  crystals.  It 
is  certain  that  the  sugar-losses  brought  about  by  such  a  treat- 
ment in  the  centrifugals  are  greater  and  the  yield  smaller  than 
when  the  meal  is  removed  by  treatment  in  crystallizers  or 
mixers. 


CHAPTER  XVIII. 
RAW  SUGAR  AND  ITS   PREPARATION. 

Raw  sugar  is  obtained  simply  by  the  centrifugation  of  the 
massecuite.  In  the  case  of  "firsts"  the  centrifugals  are  filled 
while  not  in  motion,  and  as  much  massecuite  is  placed  in  them 
as  their  construction  and  strength  will  permit  working  satisfac- 
torily. The  greater  the  quantity  of  the  massecuite  introduced 
the  more  raw  sugar  will  be  obtained  from  each  centrifugal, 
because  a  very  considerable  part  of  the  timers  spent  in  filling 
and  discharging,  and  this  time  is  practically  the  same  irrespec- 
tive of  the  extent  of  filling.  In  the  manufacture  of  raw  sugar, 
therefore,  centrifugals  of  large  diameter  and  capacity  are  suitable, 
and,  if  these  are  provided  with  an  underdischarge,  the  amount  of 
labor  can  be  greatly  lessened. 

Raw  sugar,  as  it  comes  from  the  centrifugals,  consists  of  pure 
or  almost  pure  sugar-crystals  and  a  sirup  whose  composition  is 
identical  with  the  purgings.  Evidently  this  sirup  is  the  same 
as  that  which  surrounded  the  crystals  of  the  massecuite,  and  hence 
at  the  finishing  temperature  of  the  pan  was  still  more  or  less 
supersaturated.  This  supersaturation  increases  also  as  the  sugar 
cools  in  storage  arid  still  more  by  its  drying  in  the  carriers  and  the 
sieves. 

It  would  seem  logical  that  crystallization  out  of  this  sirup 
would  continue  while  the  sugar  was  in  storage,  as  the  conditions 
are  excellent  for  a  rapid  and  extensive  crystal  formation  from  the 

207 


208  BEET-SUGAR  MANUFACTURE. 

supersaturated  sirup,  there  being  present  a  great  excess  of  crystal 
nuclei,  6-12  times  the  weight  of  the  sirup.  The  average  thick- 
ness of  the  sirup  film  on  the  crystals  is  only  0.01-0.02  mm.  (.0004- 
.0008  inch),  a  very  minute  layer,  which  would  naturally  lead  one 
to  assume  that  an  after  crystallization  always  occurred. 

As  a  matter  of  fact,  this  crystal  increase  never  is  found.  Sirup 
washed  from  raw  sugar  crystals  by  reliable  methods  is  unchanged 
and  shows  exactly  the  same  purity  as  the  purgings,  namely,  70-80, 
while  its  supersaturation  coefficient  has  risen  at  the  room  tem- 
perature from  1.5  to  1.8. 

There  is  no  explanation  for  this  remarkable  phenomenon  other 
than  that  the  great  viscosity  of  the  sirup,  increased  by  the  super- 
saturation  induced  by  the  rapid  cooling,  prevents  crystallization 
in  spite  of  the  presence  of  so  many  crystal  nuclei. 

A  proper  yield  of  raw  sugar  can  be  obtained  from  any  good 
massecuite,  as  the  only  difference  between  one  and  another  lies 
in  the  proportion  of  crystals  to  sirup. 

The  question  as  to  the  advantage  of  preparing  raw  sugar  of  a 
greater  or  less  purity  depends  upon  the  prices  which  can  be  ob- 
tained for  each  grade.  When  the  increase  of  the  price  for  one 
degree  of  greater  purity  is  more  than  one  per  cent  of  the  bottom 
price  a  calculation  will  always  be  in  favor  of  producing  the  better 
sugar.  At  the  same  time  it  must  be  remembered  that  in  the 
preparation  of  the  better-quality  sugar  more  centrifugals  are 
required  and  more  final  sirup  is  obtained;  in  other  words,  it  must 
be  considered  whether  the  factory  is  adapted  to  the  production 
of  the  product  desired. 

The  quality  of  the  sugar,  or,  in  other  words,  the  readiness  with 
which  it  can  be  converted  into  salable  products,  depends  not  only 
upon  the  percentage  of  sucrose  which  it  contains  but  also  upon 
its  outward  characteristics,  and  in  particular  upon  having  the 
crystals  sharp,  brilliant,  and  of  uniform  size  and  whiteness,  and 
the  adhering  sirup  not  too  viscid  and  free  as  possible  from  tiny 
crystals  of  sugar.  For  the  preparation  of  certain  grades  of  sugar 
quite  large  crystals  are  required.  It  would  seem  desirable  that 
all  of  these  requirements  should  be  considered  in  estimating  the 


RAW  SUGAR  AND  ITS  PREPARATION.  209 

value  of  a  given  raw  product,  but  up  to  the  present  time  no  method 
has  been  discovered  which  will  give  results  that  are  satisfactory 
to  the  trade.  Paying  for  the  sugar  according  to  the  percentage 
of  ash  by  no  means  meets  the  actual  requirements,  for  the  yield 
in  refined  sugar  depends  not  only  upon  the  ash  but  also  upon  the 
organic  non-sugars,  and  chiefly,  in  fact,  upon  the  nature  of  the 
sugar  itself.  All  propositions,  however,  in  the  nature  of  offering 
a  more  just  valuation  of  the  raw  product  have  miscarried,  on  account 
of  the  unreliability  of  the  methods  of  examination  or  the  uncer- 
tainty of  results  obtained  by  analysis,  so  that  the  relatively  more 
accurate  determination  of  the  ash  has  been  deemed  most  satis- 
factory by  the  trade  and  has  not  been  given  up. 

Good  raw  sugar  which  is  suitable  for  the  preparation  of  the 
grades  in  daily  use  will  always  be  obtained  if  the  juices  are  good, 
well  boiled,  and  the  working  up  of  the  massecuite  is  carried  out 
with  care,  as  shown  by  its  passing  well  through  the  centrifugal 
machines  at  normal  temperature.  A  raw  sugar  which  is  cen- 
trifugated  with  difficulty  is  always  hard  to  refine,  especially  when 
boiled  by  taking  in  large  quantities  of  reworked  sirup  and  where 
mother-sirup  is  highly  dcsugarized. 

The  color  of  raw  sugar  is  not  always  a  reliable  indication 
of  its  value;  although  in  general  a  lighter  sugar  will  be  preferredr 
yet  it  ought  to  be  determined  whether  this  is  the  natural  colorr 
or  whether  it  has  been  produced  artificially  by  means  of  decoloriz- 
ing agents.  Furthermore,  the  color  of  the  sirup  which  causes  the 
color  of  the  raw  sugar  is  of  less  importance  than  the  color  of  the 
crystals  themselves,  and  not  infrequently  it  will  be  found  that 
crystals  which  are  coated  with  dark-colored  sirup  are  really  lighter 
than  those  coated  with  a  light-colored  sirup.  If  the  crystals  are 
not  pure  white  they  are  better  when  of  a  pale  yellow  than  a  grayish 
tone,  for  in  refining  the  yellow  color  is  readily  removed  by  the 
charcoal  or  covered  up  by  bluing,  so  that  the  finished  sugar  is  of  a 
better  shade  than  when  the  raw  sugar  is  gray.  The  cause  of  the 
gray  coloration  is  a  slight  iron-content  of  the  juices  which  results 
from  an  unsatisfactory  carbonatation.  Iron  salts  pass  into  solu- 
tion or  remain  dissolved  when  the  second  carbonatation  is  some- 


210  BEET-SUGAR  MANUFACTURE. 

what  incomplete  so  that  some  calcium  sucrate  remains  in  solution , 
or  when  the  carbonatation  is  carried  too  far.  Juices  which  when 
thick  or  thin  were  saturated  to  an  acid  reaction  will  always  con- 
tain iron,  and  sugar  prepared  from  them  frequently  offers  serious 
difficulties  to  the  preparation  of  a  pure  white  refined  product. 
Hence  gray  sugars  are  always  acid  to  phenolphthalein.  Carbonic- 
acid  gas  containing  hydrogen-sulphide  gas  is  also  said  to  cause  the 
formation  of  a  gray  sugar,  but,  if  so,  this  is  due  to  the  presence 
of  a  small  amount  of  iron  sulphide  remaining  dissolved  in  the 
juices. 

It  is  also  a  requisite  of  good  raw  sugar  that  it  does  not  undergo 
change  in  storage.  This  is  the  case  when  the  sugar  shows  an 
alkaline  reaction  with  phenolphthalein,  when  it  is  free  from  the 
germs  that  cause  sugar  to  invert,  and  also  free  from  easily  de- 
composable organic  non-sugars.  Alkaline  massecuites  are  always 
obtained  from  well-defecated  and  alkaline  juices,  and  consequently 
yield  a  sugar  which  keeps  well  if  the  sirup  is  sufficiently  super- 
saturated and  remains  supersaturated  while  kept  in  dry  and  cool 
places;  for,  in  such  cases,  bacteria  cannot  very  well  get  into  the 
sirup  or  still  less  can  they  develop  in  it.  When,  however,  a 
raw  sugar  is  stored,  which  contains  so  much  moisture  that  the 
sirup  in  it  is  barely  supersaturated  or  if  the  sirup  becomes 
more  dilute  during  the  storage  because  of  absorbing  water  from 
a  damp  atmosphere,  there  is  always  danger  of  both  the  alkalinity 
and  polarization  becoming  less.  Juices  which  have  been  treated 
with  sulphurous  acid,  other  things  being  equal,  yield  more  stable 
sugars  than  those  which  have  not  been,  for,  in  the  former,  a 
small  amount  of  sulphurous  acid  is  retained  which  acts  as  an 
antiseptic. 

The  form  and  sharpness  of  the  crystals  depends  not  alone  upon 
the  amount  but  upon  the  nature  of  the  non-sugars.  Juices  which 
have  been  well  treated  with  lime  always  give  better  and  harder 
crystals  than  those  which  have  been  merely  superficially  defecated. 
With  equal  purity  of  juices  the  sugar  obtained  from  fresh  beets 
at  the  beginning  of  the  campaign  always  has  a  better  grain  than 
that  obtained  towards  the  end  of  the  season  from  stored  beets. 


RAW  SUGAR  AND  ITS  PREPARATION.  211 

Certain  lime  salts  appear  to  have  a  particular  action  upon  the  crys- 
tallization, and  especially  those  which  collect  in  the  juices  when 
a  molasses  desugarizing  process  is  used.  The  sugar  obtained  from 
such  juices,  and  in  particular  the  after-product,  is  likely  to  exhibit 
crystals  of  a  pointed  or  needle  shape. 

The  raw  sugar,  as  it  is  discharged  from  the  centrifugal  machines, 
is  warm  and  by  no  means  homogeneous;  it  is  first  cooled  off, 
sifted,  and  mixed  before  it  is  ready  to  be  stored. 

The  transportation  of  the  sugar  horizontally  or  on  a  slight 
incline  is  best  accomplished  by  means  of  properly  constructed 
drag  conveyors,  for  in  this  way  the  crystals  are  not  injured  as  they 
may  be  by  screw  conveyors.  Such  carriers  are  almost  universally 
employed  under  or  at  the  centrifugals;  they  carry  the  sugar 
to  the  bucket  elevators  and  the  latter  in  turn  bring  it  to  the 
sieves. 

For  sifting  sugar,  drum-  or  shaking-sieves  are  employed.  Al- 
most any  sort  of  a  sieve  may  be  used  for  a  centrifugated  sugar 
which  is  dry  and  is  of  high  purity,  while,  on  the  other  hand,  the 
moist  88°  product  is  so  sticky  that  it  presents  more  or  less 
difficulty.  For  the  latter  sugars  shaking-  or  drum-sieves  are 
most  suitable  and  are  made  of  circular,  bent  wires,  whose  inter- 
spaces are  kept  open  by  means  of  brushes  or  prongs.  Inasmuch 
as  the  stickiness  of  the  sugar  increases  with  cooling  the  sieves 
are  arranged  to  keep  the  mass  from  rapid  cooling  by  drafts  of 
air.  The  size  of  the  interspaces  between  the  separate  wires  depends 
entirely  upon  the  nature  of  the  sugar  which  is  to  be  sifted,  but  at 
all  events  it  is  not  advisable  to  make  them  so  close  together 
that  tiny  scales  and  lumps  cannot  pass  through. 

It  is  necessary,  therefore,  to  prevent  as  much  as  possible  the 
formation  of  any  of  these  lumps  in  the  sugar.  Besides  the  scales 
which  are  formed  in  the  vacuum-pan,  the  prevention  of  which 
has  been  described  already,  it  is  possible  to  form  lumps,  which 
will  not  permit  of  centrifugation,  both  in  the  open  mixers  and  in 
the  arrangements  for  the  transportation  of  the  massecuite.  Lumps 
result  from  the  drying  of  moist  sugar  or  massecuite  on  the  upper 
surface;  these  subsequently  fall  off  in  smaller  or  larger  pieces. 


212  BEET-SUGAR  MANUFACTURE. 

The  crystals  in  these  lumps,  unlike  those  produced  in  the  boiling  ap- 
paratus, are  not  fused  together,  so  they  can  be  separated  from  one 
another  by  mashing  for  a  long  time  with  hot  sirup,  and  are  then 
suitable  for  centrifugation. 

The  sugar  which  has  been  centrifugaled  well  from  carefully 
boiled  massecuite,  which  has  subsequently  been  worked  up  well 
in  closed  crystallizers,  scarcely  requires  any  sifting.  Inasmuch, 
however,  as  the  sifting  also  serves  to  thoroughly  mix  the  sugar 
it  should  never  be  omitted. 

The  sifted  sugar  is  either  placed  in  bags  or  stored  loose.  Usually 
the  product  has  cooled  sufficiently,  in  its  passage  through  carriers 
and  sieves,  unless  the  massecuite  is  centrifugated  very  hot,  so 
that  it  is  ready  to  be  stored.  Under  no  circumstances  should 
sugar  be  stored  in  a  warm  condition,  and  particularly  not  in 
heaps,  for  in  such  cases  it  may  heat  up  still  further;  when  this 
takes  place  dark  sugar  is  found  at  those  parts  which  are  hottest 
and  the  alkalinity  is  greatly  diminished,  while  in  some  cases  it 
contains  invert-sugar.  This  phenomenon  is  an  oxidation  and  is 
brought  about  by  the  presence  of  certain  organic  non-sugars. 
When  sugar  on  leaving  the  sieves  is  still  warm  it  must  be  allowed 
to  cool  in  small  heaps  and  afterwards  placed  in  bags  or  stored 
loose. 

When  the  sugar  is  bagged  the  weight  of  the  stored  sugar  is 
accurately  determined;  in  the  case  of  sugar  stored  loose  the 
barrows  in  which  it  is  transported  are  counted  and  weighed. 
Usually  this  process  is  not  done  with  sufficient  supervision,  so  that 
as  a  result  the  weight  of  the  sugar  that  is  stored  rarely  agrees 
with  the  weight  which  is  finally  sent  away.  The  determination 
of  the  amount  of  sugar  from  the  size  of  the  heaps  never  gives 
accurate  results,  for  the  amount  of  space  occupied  by  a  given 
weight  of  sugar  depends  upon  the  size  of  the  grain  and  the  nature 
of  the  raw  sugar,  while,  finally,  the  height  of  the  different  heaps 
varies  greatly. 

In  order  to  save  labor  the  storage-room  is  placed  high  up  and 
the  sugar  is  carried  up  in  wheelbarrows  on  elevators,  or  by  means 
of  bucket  conveyors.  When  the  sugar  is  stored  loose  it  is  simply 


RAW  SUGAR  AND  IT*  PREPARATION.         213 

(lumped  out  from  the  barrows  on  the  floor,  or  it  falls  from  suita- 
bly arranged  shoots;  when  it  is  bagged  it  is  also  easier  to  fill  them 
from  above. 

Too  great  pressure  upon  the  walls  should  be  avoided  in  every 
case.  If  the  sugar  is  heaped  up  high  the  walls  must  be  very 
strong  and  well  supported.  When  the  sugar  is  in  bags  these  should 
not  be  placed  against  the  walls,  and  the  bags  should  be  laid  alter- 
nately lengthwise  and  then  crosswise,  so  that  the  pile  is  stable, 
and  there  is  no  danger  of  the  bags  sliding  when  the}'  are  being 
shipped. 

Sugar  stored  in  bags  always  keeps  better  than  in  heaps. 
Generally,  the  keeping  quality  of  sugar  depends  on  how  free  the 
sirup  is  from  infection  by  molds.  All  conditions  which  favor 
this  infection  and  the  growth  of  molds  act  to  injure  the  keeping 
qualities  of  the  sugar.  It  is  exceptional  to  find  molds  hi  sugars 
alkaline  to  phenolphthalein  which  is  characteristic  of  those  of 
proper  and  intelligent  manufacture.  The  alkalinity  alone  is 
not,  however,  a  protection  against  destructive  changes  in  sugar. 
Cool  and  equable  temperature,  as  little  moisture  as  possible  in 
tin-  sugar,  and  a  hi;h  concentration  of  the  s.rup  adhering  to 
the  crystals  arc  all  hostile  to  the  growth  of  molds. 

The  storeroom  should  be  cool  and  dry.  As  far  as  possible 
warm  places,  or  those  into  which  the  hot  and  moist  air  from  the 
factory  penetrates,  should  not  be  chosen  for  storing  sugar.  In  the 
former  case  the  sugar  dries  and  besides  losing  in  weight  it'becomes 
less  suitable  for  refining,  because  the  sirup  in  the  crystals  is  then 
more  viscid.  In  moist  places,  on  the  other  hand,  the  sugar  attracts 
moisture  and  easily  becomes  so  moist  that  the  sirup  runs  off  from 
the  crystals,  the  micro-organisms  develop  in  it  and  cause  the 
inversion  of  some  of  the  sugar.  The  sirup  may  later  run  through 
the  sacks  or  from  sirup-stripes  in  the  heaps.  When  the  storage- 
place  is  cool  and  dry  there  is  never  any  separation  of  sirup  from 
the  crystals  if  the  sugar  has  been  properly  purged,  even  when 
it  is  only  of  88°  quality,  for  the  sirup  adhering  to  the  crystals 
at  the  low  temperature  is  so  viscous  on  account  of  its  supersatura- 
tion  that  it  adheres  as  a  film  on  the  crystals. 


CHAPTER  XIX. 
THE  PREPARATION  OF  SUGAR   CRYSTALS. 

MANY  factories,  instead  of  stopping  with  the  preparation  of  the 
raw  sugar,  manufacture  a  product  which  can  be  directly  utilized, 
and  they  accomplish  this  by  removing  all  the  sirup  from  the 
crystals.  In  this  way  a  crystallized  sugar  (granulated)  is  ob- 
tained, or  powdered  sugar,  or  sugar  loaves  (Pilee)  but  these 
products  are  not  to  be  regarded  in  any  respect  as  refined  sugar, 
although  perfectly  suitable  for  many  purposes.  Refining  is  brought 
about  by  a  dissolving  and  purifying  process. 

The  preparation  of  sugar  crystals  from  the  massecuite  is  ac- 
complished in  the  first  place  exactly  as  in  the  case  of  raw  sugar, 
but  as  much  of  the  sirup  is  removed  as  possible  by  centrifugation ; 
to  accomplish  this  the  massecuite  is  not  allowed  to  cool  very  much. 
The  sirup  that  is  not  removed  in  this  way  is  washed  out  by  means 
of  water,  steam,  or  saturated  sugar-solution,  and  in  such  a  way 
that  as  little  sugar  is  dissolved  as  possible.  In  order  to  improve 
the  color  a  little  ultramarine  is  added  in  the  vacuum-pan  and 
also  to  the  wash-liquids.  The  ultramarine  used  should  be  of  a 
good  quality  and  carefully  prepared,  otherwise  the  sugar  will  be 
of  a  bad  color. 

Only  good  juices  can  be  used  to  advantage  for  the  manufacture 
of  this  grade  of  sugar.  When  the  ordinary  sirups  are  not  pure 
enough  they  are  often  improved  in  quality  by  the  introduction 
of  a  little  of  the  after-product  sugar.  Naturally  more  weight  is 
laid  upon  the  production  of  a  uniform  grain  and  a  careful  working 

214 


THE  PREPARATION  OF  SUGAR  CRYSTALS.  215 

up  of  the  massecuite  than  when  simply  a  raw  sugar  is  to  be  made ; 
it  is  not  possible  to  prepare  good  sugar-crystals  in  this  way  from 
a  massecuite  which  does  not  act  well  in  the  centrifugal  machines. 

For  the  manufacture  of  the  sugar-crystals  centrifugals  of 
large  diameter  are  suitable,  although  it  is  advisable  to  fill  them  to  a 
less  extent  than  in  the  former  case,  so  that  the  layer  of  sugar  rest- 
ing against  the  strainer  is  less  thick  and  can  be  washed  more 
uniformly. 

When  saturated  pure  sugar-solutions  are  used  as  clearing  sirups 
for  removing  sirup  from  the  crystals  while  they  are  in  the  centrif- 
ugals none  of  the  latter  will  dissolve,  and  all  of  the  crystallized 
sugar  will  be  converted  into  the  desired  product.  But  since  a 
part  of  the  product  must  be  used  in  the  preparation  of  the  wash- 
liquid,  or  clarifier,  and  when  once  used  it  becomes  so  contam- 
inated with  sirup  that  it  cannot  be  used  over  again  for  clearing,  it  is 
evident  that  the  actual  yield  of  sugar  is  considerably  diminished. 

In  the  beet-sugar  factories  pure  sugar-solutions  are  seldom  used 
as  clarifiers,  but  usually  the  crystals  are  treated  with  water  or 
steam,  and  frequently  both  are  used  together.  In  this  case,  also, 
it  is  necessary  to  use  the  water  or  steam  in  such  a  way  that  as 
little  as  possible  of  the  sugar  is  dissolved  out  during  the  process. 
The  water  is  introduced  in  as  finely  divided  a  condition  as  possible 
by  means  of  a  rose,  or,  still  better,  it  is  sprayed  in  by  compressed 
air.  The  condensed  water  is  removed  from  the  steam  before  in- 
troducing it  into  the  drum,  or  it  is  superheated,  and  the  upper 
opening  of  the  centrifugal  is  closed  by  a  cover,  so  that  there  is 
no  condensation  by  the  steam  coming  in  contact  with  the  outside 
air.  In  all  cases  the  water  or  steam  will,  despite  all  precautions, 
dissolve  away  a  little  of  the  sugar  from  the  crystals,  or  else  it  will 
not  remove  all  of  the  sirup.  After  or  during  the  washing  of  the 
crystals  with  water,  steam  is  often  introduced,  and  in  this  case 
it  is  well  to  make  use  of  the  so-called  Russian  steam-mantle,  in 
which  case  the  steam  is  introduced  between  the  mantle  and  the 
drum.  The  chief  action  of  the  steam  is  then  to  warm  up  the  con- 
tents of  the  drum,  and  without  the  condensation  of  any  considerable 
amount  of  water  upon  the  sugar.  The  Russian  steam-mantle  is, 
as  already  mentioned,  also  used  to  advantage  in  the  preparation 


216  BEET-SUGAR  MANUFACTURE. 

of  raw  sugar  or  the  after-products,  because  it  prevents  the  sirup 
from  becoming  too  viscous  in  consequence  of  too  great  a  cooling. 
The  steam  should  not  be  directed  against  the  drum,  because 
in  such  cases  those  parts  of  the  drum  which  the  steam  or  water 
strikes  against  suffer  in  the  course  of  time.  Consequently  the 
steam  is  directed  against  a  sheet  of  metal  which  serves  to  turn 
the  direction  of  the  vapor  to  one  side  and  distributes  it  uniformly 
throughout  the  apparatus. 

Frequently,  before  washing  the  crystals  with  water  or  steam, 
they  are  covered  with  the  so-called  covering-sirup,  the  latter  being 
made  up  of  the  liquid  thrown  off  by  the  centrifugals  in  the  last 
washing  of  the  previous  lot  of  crystals,  or  of  sirup  which  has  been 
evaporated  to  the  saturation  point.  By  .means  of  these  liquids 
first  of  all  the  green  sirup  is  displaced;  the  lighter  sirup  or 
thick  juice  then  adheres  to  the  crystals,  and  either  of  these  latter 
can  be  removed  with  materially  less  steam  or  water.  When  this 
method  of  preliminary  covering  is  used  the  process  becomes 
somewhat  more  involved,  and  it  is  a  matter  for  calculation  to  deter- 
mine whether  the  increased  sugar-yield  compensates  for  the  extra 
trouble.  The  advantages  to  be  gained,  even  when  these  preliminary 
covers  are  particularly  clear  and  pure,  are  at  all  events  not  very 
great.  Since  some  sugar  will  be  dissolved  from  the  crystals  in  every 
case  when  pure,  white  crystals  are  to  be  obtained,  the  chief  require- 
ment for  a  good  yield  is  the  careful  separation  of  the  sirup  purg- 
ings,  according  to  their  purity,  so  that  the  better  portions  can 
be  again  boiled  down  with  the  thick  juice  for  the  production 
of  sugar-crystals.  The  first  portion  of  sirup  centrifugaled  is 
the  so-called  "green  sirup"  which  in  the  ordinary  method  is 
collected  by  itself,  sometimes  being  thinned  by  steam.  The 
sirup  that  is  next  obtained  in  the  covering  process  is  at  first  carried 
off  in  the  green-sirup  gutter,  but  as  soon  as  it  becomes  lighter 
colored,  showing  covering-sirup,  it  is  run  into  a  different  gutter 
and  either  carried  back  directly  to  the  thick  sirup,  or  it  is  added 
by  itself  to  the  vacuum-pans  during  the  boiling  process. 

For  the  separation  of  the  covering-sirup  according  to  its  purity 
there  are  a  number  of  different  devices  in  use.  It  is  important 


THE   PREPARATION  OF  SUGAR  CRYSTALS.  217 

for  the  simpler  forms,  in  which  the  separation  takes  place  outside 
the  centrifugal  machines,  that  the  centrifugation  of  each  filling 
should  not  be  accomplished  in  too  ^hort  a  time,  so  that  one  grade 
of  sirup  will  run  off  sufficiently  before  a  second  quality  is  thrown 
off,  the  green  sirup  being  removed  when  the  covering  process 
begins  and,  conversely,  the  better  covering-sirup  run  off  when 
the  centrifugals  are  filled  with  fresh  massecuite.  In  the  case 
of  large  centrifugal  machines  which  must  run  for  a  longer  time 
the  separation  of  the  sirup  is  better  than  in  the  smaller  ones. 
In  other  methods  of  separation  the  sirups  of  different  degrees 
of  purity  are  separated  in  the  casing  of  the  centrifugal  apparatus 
itself,  so  that  here  the  separation  is  a  sharp  one,  to  the  exten^ 
that  it  is  possible  to  remove  the  sirup  by  centrifugation.  In 
this  way  the  centrifugal  work  is  accelerated.  Even  here,  how- 
ever, more  centrifugal  are  required  in  the  manufacture  of  the 
sugar-crystals  than  when  merely  the  raw  sugar  is  produced. 

The  further  treatment  of  washed  sugar-crystals  depends  upon 
the  product  which  it  is  desired  to  manufacture.  Granulated  and 
crystal-sugar  must  leave  the  centrifugals  in  a  warm  and  somewhat 
moist  condition,  so  that  the  crystals  do  not  bake  together  to  form 
solid  pieces,  whereas,  in  the  manufacture  of  the  Pilee  (loaf)  sugar 
this  cementing  is  desirable.  When  the  crystals  have  been  pre- 
pared by  washing  with  steam  it  is  not  necessary  to  have  any 
particular  arrangement  for  drying  them,  for  this  is  sufficiently 
accomplished  during  the  transportation  and  sifting  of  the  product. 
In  case  the  crystals  have  been  washed  with  water  they  must 
be  dried  in  drums  or  granulators.  When  a  product  of  uniform 
grain  is  desired  it  must  be  sifted.  The  smaller  crystals,  or  some- 
times the  whole  product,  are  frequently  powdered.  It  is  im- 
portant that  even  these  sugar-crystals,  as  in  the  case  of  the  raw 
sugar,  must  be  thoroughly  cooled  before  they  are  sacked  or  stored, 
as  otherwise  the  sugar  is  apt  to  get  a  yellow  coloration.  In  the 
preparation  of  Pilee,  centrifugals  of  an  especial  design  are  em- 
ployed which  provide  for  the  easy  removal  of  the  hard  loaves. 

Another  method  for  preparing  white  crystals  from  the  massr- 
cuite  is  the  massecuite  wash.  The  massecuite,  being  brought 


218  BEET-SUGAR  MANUFACTURE. 

to  the  proper  point  in  the  vacuum-pans,  is  cooled  to  40°  or  50° 
(104-122°  F.)  in  the  crystallizers,  and,  finally,  diluted  till  the 
mother-sirup  is  only  slightly  supersaturated.  Under  no  cir- 
cumstances should  there  be  fine  crystals  or  crystalline  meal,  but 
a  uniformly  good  grain  should  be  obtained.  The  massecuite  is 
placed  in  large  rectangular  or  oval  tanks  provided  with  sieves  at 
the  bottom,  and  the  sirup  draining  off  is  sucked  away  by  means 
of  a  pump.  As  soon  as  the  first  sirup  has  been  drained  off  as 
completely  as  possible,  one  that  is  purer  is  poured  over  the 
mass  and  this  is  likewise  drained  off,  the  operation  being  repeated 
three  or  four  times  with  sirups  of  constantly  increasing  purity. 
The  sirups  first  used  come  from  the  previous  coverings,  but  in  the 
last  case  a  pure  sugar-solution  is  used;  either  such  a  solution  is 
prepared  or  else  pure  water  is  added,  which  dissolves  enough 
sugar  from  the  crystals  to  become  saturated. 

Particular  stress  must  be  laid  upon  the  importance  of  sepa- 
rating the  sirup  well  after  each  covering.  The  first  sirup  has  a 
purity  of  70  to  75.  This  is  taken  out  of  the  process  and  no 
longer  used  for  washing.  The  second  sirup  serves  for  the  first 
cover  of  the  next  massecuite  and  so  on.  The  sirup  is  run  into 
cells  or  into  ordinary  tanks,  in  which  the  supersaturated  sirup 
that  has  drained  off  at  the  beginning  can  be  diluted  to  the  proper 
concentration  with  water. 

Since  the  temperature  in  the  wash-room  is  quite  different  at 
different  seasons  of  the  year  it  is  not  possible  to  prescribe  once 
for  all  time  any  definite  density  for  wish-sirups,  but  this  density 
must  be  governed  by  the  prevailing  temperature,  so  that  the  sirups 
used  will  be  saturated  with  sugar  in  all  cases,  and  not  supersaturated 
at  one  time  and  undersaturated  at  another.  The  temperature  in 
the  wash-room  should  not  fall  below  20°  C.  (68°  F.),  because  at 
temperatures  lower  than  this  the  viscosity  of  the  sirup  increases 
very  considerably  and  the  washing  will  then  require  a  much  greater 
length  of  time;  it  is  advisable  that  the  room  should  be  heated 
in  winter.  In  the  same  sense  any  supersaturation  of  the  wash- 
sirups  acts  detrimentally,  wherea<,  on  the  other  hand,  although 
undersaiurated  juices  effect  a  much  more  rapid  washing  they 
dissolve  sugar,  and,  consequently,  lessen  the  yield.  Only  when 


THE   PREPARATION"  OF  SUGAR  CRYSTALS.  219 

the  maaeecuite  contains  a  strongly  supersaturated  sirup  is  it 
desirable  to  use  for  the  first  cover  an  undersaturated  wash  which 
will  become  a  saturated  liquid  when  mixed  with  the  supersaturated 
sirup,  thus  accelerating  the  washing  without  dissolving  any  sugar 
from  the  mass.  It  is  naturally  preferable  to  work  up  the  masse- 
cuites  in  the  crystallizers  so  that  the  mother-sirup  will  form  simply 
a  saturated  solution. 

The  yield  of  white  crystals  is  greater  by  this  method  than  when 
cent rifugat ion  is  employed,  because  a  green  sirup  of  lower  purity 
is  in  each  case  removed  from  the  process.  This  result,  however, 
is  obtained  only  after  the  expenditure  of  considerable  time. 

A  further  disadvantage  of  the  washing  method:  If  a  sirup  is 
used  for  a  relatively  great  length  of  time  before  it  is  thrown  out 
there  is  a  possibility  of  its  changing.  At  all  events  it  is  necessary 
to  exercise  the  greatest  care  to  avoid  all  causes  for  inver- 
sion of  the  sugar.  Great  cleanliness  is  required  above  all  things, 
and  sirups  should  also  show  the  desired  amount  of  alkalinity. 
This  alkalinity  is  maintained  by  the  addition  of  soda  rather  than 
lime.  When  inversion  of  sugar  sets  in  toxany  extent  the  only 
remedy  is  to  carefully  clean  all  tanks  and  cells  and  start  the  work 
afresh. 

If  the  sugar  obtained  by  washing  is  to  be  worked  up  into 
crystals  it  must  be  centrifugated  and  then  dried.  Usually  this 
washing  process  is  only  for  the  purpose  of  obtaining  crystals  that 
are  suitable  for  refining;  in  such  cases  the  crystals  are  dissolved 
directly  in  the  tanks. 


CHAPTER  XX. 
WORKING  UP  CENTRIFUGAL  SIRUP  INTO  AFTER-PRODUCTS. 

THE  main  object  in  working  up  centrifugal  sirup  from  the  first 
products  is  to  obtain  all  the  sugar  possible  in  crystal  form,  but 
not  with  too  fine  a  grain,  so  that  the  mother-liquor  eventually 
obtained  is  a  true  molasses. 

This  end  is  attained  in  different  ways:  first  of  all  the  sirup 
must  be  thickened  or  boiled  down.  For  this  purpose  a  vacuum- 
pan  is  used  which  is  of  the  same  construction  as  that  used  for 
boiling  the  concentrated  juice;  one  heated  by  means  of  pipes, 
arranged  vertically  or  inclined  and  of  large  diameter,  being  pre- 
ferred. For  the  thickening  of  the  sirup  and  the  management  of 
the  apparatus  the  same  directions  and  rules  hold  that  were  given 
for  boiling  juice,  except  in  so  far  as  they  were  applicable  only  to 
juices  of  high  purity.  It  is  particularly  important  to  make  sure 
of  good  sirup  circulation,  that  the  sirup  is  well  warmed,  enters 
in  the  lower  part  of  the  apparatus,  and  that  the  heating  is  by 
means  of  low-pressure  steam. 

There  are  three  principal  processes  for  working  up  centrifugal 
sirup. 

1.  Blank  boiling  of  the  sirup,  subsequently  allowing  the  sugar 
to  crystallize  out  in  tanks,  with  or  without  the  addition  of  ex- 
citing crystals. 

2.  Blank  boiling  of  the  sirup  and  working  up  the  massecuite 
in  crystallizers,  in  which  the  crystals  are  either  formed  by  cool- 
ing or  ready  formed  crystals  are  added. 

3.  Boiling  the  sirup  to  grain,  or  with  the  addition  of  exciting 
crystals,  and  further  working  up  of  the  massecuite  in  crystallizers. 

220 


AFTER-PRODUCTS  OF  CENTRIFUGAL  SIRUP.  221 

By  all  of  these  methods  of  working  the  complete  crystallization 
of  the  sugar  up  to  the  formation  of  true  molasses  can  be  effected, 
but  the  length  of  time  required  is  different.  It  is  assumed,  of 
course,  that  in  each  case  the  process  is  correctly  carried  out. 

In  the  proper  working  up  of  centrifugal  sirup  the  correct  con- 
centration and  temperature  should  be  maintained  during  the 
whole  period  of  crystallization,  and  those  conditions  established 
which  are  favorable  for  crystallization.  Exactly  as  in  the  prepara- 
tion and  treatment  of  the  massecuite  of  the  firsts  here,  again , 
in  working  the  massecuite  from  the  sirup  a  definite  supersatura- 
tion  is  most  favorable,  but  this  depends  upon  the  purity  and  the 
temperature.  Too  great  supersaturation,  especially  in  the  case  of 
pure  sirups,  tends  to  form  new  and  fine  crystals  at  the  time  when 
it  is  not  desirable  that  any  more  crystals  should  form,  and  so  tends 
to  retard  or  prevent  the  desired  crystallization,  and  particularly  at 
low  temperatures,  on  account  of  the  greater  viscosity  of  the  sirup 
Too  low  supersaturation,  on  the  other  hand,  makes  crystallization 
take  place  much  more  slowly,  especially  in  the  case  of  impure  sirups. 

Only  when  centrifugal  sirup  is  boiled  to^grain,  or  with  exciting 
crystals,  can  the  concentration  be  constantly  maintained  at  the 
supersaturation-coefficient  which  is  known  to  be  the  most  favor- 
able. In  the  case  of  all  the  other  methods  of  working  the  process 
should  be  conducted  so  that  the  mother-liquor  remains  supersat- 
urated up  to  the  last,  that  is,  until  all  the  crystallizable  sugar  has 
separated  out.  Such  a  massecuite  will  consist  of  sugar-crystals 
and  an  actual  molasses  in  a  saturated  or  slightly  supersaturated 
condition. 

The  supersaturation  ratios  of  impure  centrifugal  sirups  are 
not  as  simple  as  in  the  case  of  the  pure  sirups.  Whereas,  in  the  lat- 
ter, the  coefficient  may  be  assumed  to  be  practically  the  same  as  in 
the  case  of  pure  sugar-solutions  and  the  extent  of  supersaturation 
can  be  readily  computed  by  means  of  solubility  values  of  pure 
saturated  sugar-solutions;  in  the  case  of  sirups  the  supersatura- 
tion relations  depend  upon  the  amount  and  nature  of  the  non- 
sugars  present. 

Small  amounts  of  but  one  non-sugar  in  solution  with  sugar 


222  BEET-SUGAR  MANUFACTURE. 

lessen  the  solubility  of  the  latter,  while  larger  amounts  increase 
the  solubility.  As  a  rule,  non-sugars  which  take  up  water  of 
crystallization  diminish  the  solubility  of  sugar.  Those  which 
tend  to  increase  the  solubility  of  sugar  most  are  alkaline  salts 
of  organic  acids.  Practically  the  same  phenomena  are  observed 
in  mixtures  of  non-sugars,  in  general,  such  behave  as  the  sum 
of  the  equivalents  of  the  individual  constituents,  not  as  the  sum 
of  the  individual  influences  of  the  constituents. 

It  appears  however,  as  if  the  total  non-sugars,  in  the  sirups 
and  molasses  from  beet-sugar  manufacture,  in  spite  of  great 
variation  in  quantity,  characteristics  and  composition  always  have 
practically  the  same  influence  upon  the  solubility  of  the  sugar,  as 
long  as  the  proportion  of  ash  to  organic  non-sugar  remains  prac- 
tically the  same,  and  no  abnormal  constituents  are  present.  In 
pure  sirups  there  is  never  any  variation  in  this  solubility  influence ; 
when  it  does  appear  it  is  first  noticeable  in  molasses  liquors.  Hence 
it  is  almost  a  certainty  that  sirups  of  more  than  65  purity, 
even  of  different  crops,  will  show  practically  identical  sugar 
solubility. 

Among  the  substances  having  strong  influence  on  the  solu- 
bility of  sugar,  especially  in  molasses,  are  raffinose,  organic  lime 
salts,  particularly  those  formed  from  the  decomposition  of  invert 
sugar  by  lime,  likewise  invert  sugar  itself.  All  these  substances, 
whether  free  or  combined  in  salts  induce  sugar  crystallization, 
in  other  words,  lessen  its  solubility. 

In  order  to  prevent  any  misunderstanding  it  is  important 
to  emphasize  in  this  connection  that  these  solubility  relations  have 
in  themselves  nothing  to  do  with  the  formation  of  molasses,  as 
is  frequently  erroneously  assumed.  The  solubility  data  simply 
show  how  much  the  sirup  must  be  evaporated  in  order  to  bring 
it  to  the  crystallizing  point.  If  the  sugar  is  more  soluble  in  one 
non-sugar  than  in  another  it  is  evident  that  the  former  must  be 
evaporated  to  a  greater  extent  before  the  sugar  will  crystallize; 
this  is  assuming  that  the  liquid  is  purer  than  a  true  molasses,  for 
the  latter  can  be  evaporated  to  dryness  without  any  sugar  crystal- 
lizing out. 


AFTER-PRODUCTS    OF   CENTRIFUGAL  SIRUP.  223 

The  solubility  of  sugar  varies  with  the  temperature  and  the 
proportion  of  water  to  sugar  in  impure,  saturated  sugar  solutions 
is  quite  different  than  in  pure.  The  reason  for  this  is  that  in  the 
strong  concentrating  of  solutions  at  high  temperature,  not  only 
the  sugar-content  but  the  non-sugar-content  increases  and  conse- 
quently the  latter  exerts  greater  solvent  action  on  the  sugar. 

For  example,  a  sirup  of  62  purity  is  saturated  at  20°  (68°  F.) 
when  it  contains  for  each  part  of  water  1.15  times  as  much  sugar 
dissolved  in  it  as  a  pure  sugar-solution  saturated  at  the  same 
temperature,  that  is  to  say,  2.04x1.15  parts  of  sugar.  Then  the 
composition  of  this  sirup  is:  20.9  per  cent,  water,  49.0  per 
cent,  sugar,  30.1  per  cent,  non-sugar.  But  this  same  sirup  is 
saturated  at  70°  (158°  F.)  when  it  contains  1.5  times  as  much 
sugar  as  a  pure  sugar-solution  saturated  at  70°,  hence,  with 
1.5X3.2  parts  of  sugar,  its  composition  is:  11.4  per  cent  water, 
54.9  per  cent,  sugar,  33.7  per  cent,  non-sugar.  Accordingly  in 
the  sirup  saturated  with  sugar  at  20°  there  are  1.44  parts  of  non- 
sugar  per  part  of  water,  while  in  that  saturated  at  70°  there  are 
2.96  parts  dissolved.  This  doubling  of  the  strength  of  the  non- 
sugar  solution  accounts  for  the  increased  solubility  of  the  sugar. 

Temperature  by  itself  seems  to  have  no  influence,  on  the 
solubility  influence  of  the  non-sugar,  at  least  only  an  indirect  one, 
as  when  temperature  variation  causes  a  change  in  the  amount  of 
water  of  crystallization  combined  with  the  salts  in  solution  with 
consequent  alteration  of  the  amount  of  free  water  present. 

The  value  expressing  the  excess  of  sugar  dissolved  in  a  sirup 
per  unit  weight  of  water  over  that  in  a  saturated  solution  of  pure 
sugar,  at  the  same  temperature  is  of  great  practical  significance 
in  understanding  and  controlling  after-products.  This  figure 
is  known  as  the  "  saturation  coefficient."  It  follows  along  this 
reasoning  that  the  saturation  coefficient  for  all  sirups  is  smaller 
the  lower  the  temperature  and  greater  the  lower  the  purity,  these 
changes  always  being  results  of  concentration  variations  in  the 
non-sugars  in  solution. 

Consequently,  the  ratio  of  sugar  in  a  unit  weight  of  water  in  the 
mother  liquors  to  that  in  a  pure  sugar-solution  at  the  same  tern- 


221  BEET-SUGAR  MANUFACTURE. 

perature  is  recommended  as  the  best  control  figure  for  working 
up  after-products  in  a  practical  way.  Since  both  methods  are 
founded  on  the  same  principles  it  is  a  matter  of  preference  which 
will  be  used.  The  saturation  coefficient  seems  to  be  simpler 
and  explain  crystal  formation  better,  moreover  the  supersatu- 
ration  can  always  be  expressed  through  the  former  as  a  pro- 
portion. 

The  values  of  saturation-coefficients  of  sirups  of  different  purity 
at  different  temperatures,  in  other  words,  the  extent  of  the  in- 
fluence of  non-sugar  solutions  of  different  concentrations  on  the 
sugar  solubility,  are  not  very  well  known.  Investigations  are 
rather  difficult  to  make.  The  results  also  vary  according  to 
whether  the  saturation  is  determined  by  crystallizing  out  from  a 
supersaturated  solution  or  dissolve  the  sugar  in  a  solution  which 
is  unsaturated.  In  the  first  case  the  saturation  coefficient  is 
larger  than  in  the  latter  and  this  difference  is  greater  the  lower 
the  purity  of  the  sirup. 

For  practical  work,  the  coefficients  found  by  crystallizing 
sugar  out  from  supersaturated  solutions  are  the  correct  ones. 
From  the  few  experiments  which  have  been  made  only  approx- 
imate values  can  be  given,  but  these  are,  however,  sufficient  for 
practical  purposes. 

First  of  all  it  is  of  interest  to  show  the  saturation  relations 
in  centrifugal  sirups  of  different  degrees  of  purity  at  the  final 
temperatures  of  the  crystallization,  which  lie  betewen  40°  and 
130°  C.  (104-122°  F.)  At  these  temperatures  the  saturation- 
coefficient  is 

In  saturated  sirups  of  75  purity  about  1.0 

"         "  "     "       75-70       "  "  1.0  -1.05 

"     "       70-65       "  "  1.05-1.10 

"     "        65-60       "  "  1.10-1.25 

"  under       60       "  "  1.3 

The  saturation  conditions  in  a  centrifugal  sirup  of  about  60-62 
purity,  that  is  in  one  which  is  practically  a  molasses,  is  for  different 
temperatures  approximately  as  follows: 


AFTER-PRODUCTS  OF  CENTRIFUGAL  SIRUP. 


225 


In  One  Part  of  Water  are  Dissolved 

Temperature. 

In  a  Saturated 
Sirup  of  60-62 

In  a  Saturated 
Solution  of  Pure 

Difference. 

Saturation 
coefficient 
of  Sirup. 

Purity. 

Sugar. 

80°  C.  (176°  F.) 

5.8 

3.6 

2.2 

.6 

70°  '     (158°  ") 

4.8 

3.2 

1.6 

.5 

60°'     (140°") 

4.1 

2.9 

1.2 

.4 

50°'     (122°") 

3.4 

2.6 

0.8 

.3 

35°  '     (  95°"  ) 

2.8 

2.3 

0.5 

.2 

20°  '     (  68°"') 

2.3 

2.0 

0.3 

.15 

By  means  of  these  data  the  composition,  or  at  least  the  water- 
content  of  the  molasses-mother  liquors  can  be  calculated,  assum- 
ing crystallization  to  be  properly  carried  out  and  the  purity  of  the 
molasses  about  60.  Such  molasses  cannot  dissolve  sugar  because 
it  is  saturated,  while,  on  the  other  hand  it  will  be  the  least  hindrance 
to  crystallization,  since  its  viscosity  is  the  smallest  possible. 
Obviously  in  practice  the  molasses-mother-liquor  must  be  kept 
somewhat  supersaturated,  in  order  that  crystallization  will  go  on 
till  the  end, -and  as  a  fact  the  supersaturation-ctfefficient  is  kept 
at  from  1.05-1.10.  The  following  data  of  the  composition  of 
molasses-mother-liquors  at  different  temperatures  at  completion 
of  crystallization  give  the  highest  water-content  permissible,  but 
which  actually  in  practice  ought  not  be  any  less. 

COMPOSITION  OF  MOLASSES. 


At  a  Temperature  on 
Completing  Crystalli- 

Sucrose. 

Water. 

Non-sugars. 

Purity. 

zation  of 

35°C.(  95°  F.) 

49.4 

17.6 

33.0 

60 

50°  "  (122°  "  ) 

51.0 

15.0 

34.0 

60 

60°  "  (140°  "  ) 

52.4 

12.7 

34.9 

60 

70°  "  (158°  "  ) 

53.3 

11.1 

35.6 

60 

Moreover,  from  these  data  the  proper  concentration  can 
be  calculated  for  the  final  thickening  of  a  sirup,  which  is  boiled 
blank,  so  that  the  final  molasses  will  have  suitable  super- 
saturation.  All  that  is  necessary  is  to  make  a  calculation  of  the 
sugar  required  to  be  dissolved  in  th'j  molasses  to  bring  it  to 


226  BEET-SUGAR   MANUFACTURE. 

the  purity  of  the  sirup  and  then  reckon  the  result  as  a  percentage. 
When  sirups  are  boiled  to  grain  the  supersaturation-coefficients 
which  are  maintained  during  boiling  usually  depend  on  other 
circumstances,  which  will  be  explained  later.  The  normal  molasses 
data  only  serve  in  such  cases  to  establish  the  proper  concentration 
for  purging. 

If  the  proper  concentrations  of  sirup  and  mother-liquor  sirup 
are  used  all  the  conditions  necessary  for  best  crystallization  are 
fulfilled,  since  the  sirup  under  such  conditions  has  the  least  vis- 
cosity. 

The  viscosity  of  sirups  or  molasses  is  decidedly  a  hindrance 
to  rapid  graining,  since  the  molecules  of  dissolved  sugar  must 
overcome  the  resistance  caused  by  this  viscosity  in  order  to 
come  in  contact  with  the  crystals.  This  resistance  cannot  be 
appreciably  lessened  by  mechanical  movement  of  the  mass,  because 
the  sirup  particles  adhering  to  the  crystals,  and  out  of  which  the 
sugar  must  crystallize,  do  not  in  the  least  change  their  position 
relative  to  the  crystals.  Mechanical  movement  of  massecuite  is  of 
no  use  whatsoever,  except  to  equalize  temperature  and  concen- 
tration in  different  parts  of  the  apparatus,  while  the  maintenance 
of  uniform  concentration  around  the  crystallization  centres  depends 
on  diffusion,  which  in  turn  is  dependent  on  the  viscosity.  To 
obtain  the  most  appropriate  concentration  of  the  sirup  there  must 
be  for  the  given  conditions  the  least  possible  supersaturation,  as 
this  gives  the  least  viscosity,  for  this  latter  increases  very  rapidly 
with  the  degree  of  supersaturation.  Temperature  has  still  greater 
influence  on  viscosity.  At  temperatures  of  from  75°-90°  C.  (167°- 
194°  F.),  that  is  at  the  ordinary  boiling  temperatures  of  the 
vacuum-pan,  the  viscosity  of  sirups,  whether  of  high  or  low  purity, 
or  whether  saturated  or  quite  strongly  supersaturated,  is  prac- 
tically the  same.  If,  however,  the  temperature  falls  to  60°-65°  C. 
(140°-150°  F.)  the  viscosity  increases  much  more  in  proportion 
as  the  sirup  is  impure  or  supersaturated;  indeed,  the  viscosity  of 
impure  sirups  can  be  so  great  at  ordinary  temperatures  that  no 
crystallization  at  all  can  occur.  On  the  other  hand,  centrifugal 
sirups  can  be  supersaturated  to  a  greater  extent  the  higher  the 


AFTER-PRODUCTS  OF  CENTRIFUGAL  SIRUP.  227 

temperature,  and  the  crystallization  period  be  correspondingly 
shortened.  A  good  high  temperature  can  only  be  maintained  for 
any  length  of  time  in  vacuum-pans  or  crystallizers,  hence,  as  ex- 
perience has  shown,  crystallization  in  such  apparatus  is  decidedly 
quicker  than  working  with  wagons  or  tanks. 

Other  necessary  conditions  for  good  and  quick  crystallization 
of  centrifugal  sirup  are  uniformity  of  temperature  and  concentration 
in  all  parts  of  the  massecuite  and  a  suitable  amount  of  crystal  foun- 
dation. Uniformity  of  temperature  and  concentration  can  only 
bo  maintained  in  vacuum-pans  or  crystallizers.  Moreover,  such 
apparatus  have  the  advantage  that  the  crystal  foundation  which 
is  put  into  the  massecuite  or  formed  from  it  always  remains  uni- 
formly distributed  throughout,  and  is  therefore  best  utilized  for 
crystal  nuclei.  The  greater  the  number  of  such  nuclei  the  smaller 
the  crystals,  and  for  an  equal  weight  the  quicker  the  removal  of 
the  sugar  from  the  sirup.  For  the  manufacture  of  fine-grained 
sugars  there  is,  however,  in  practice,  a  certain  well-defined  limit 
as  to  size,  for  necessarily  the  crystals  must  be  sufficiently  formed 
at  least  to  give  no  difficulty  in  purging  or  cause  loss.  Obviously, 
too,  the  market  requirements,  or  the  use  to  which  the  sugar  is  to 
be  put,  will  be  an  important  consideration  in  the  choice  of  grain,  so 
that  it  often  is  profitable  to  add  a  decidedly  coarse  grain,  of  which 
a  much  greater  weight  will  have  to  be  used  to  desugarize  the 
sirup  well. 

Working  up  after-product  sirups  is  often  the  bugbear  of  the 
establishment,  particularly  in  beet-sugar  factories;  but  if  the 
necessary  care  and  supervision  are  spent  on  this  work,  better  yield 
and  quicker  crystallization  can  surely  be  obtained  with  no  greater 
cost  whatever,  and  these  are  certainly  important  improvements. 
The  conditions  bearing  on  this  work  have,  therefore,  been  de- 
scribed more  in  detail  than  would  otherwise  be  necessary. 

Control  hi  working  up  after-products  is  much  facilitated  by  use 
of  apparatus  showing  continuously  the  concentration  of  the  sirup 
during  boiling  in  the  vacuum-pan.  Formerly  the  thickening  was 
controlled  by  the  string-proof,  which  gave  fairly  reliable  indications 
when  made  by  a  skillful  and  reliable  sugar-boiler.  In  many  estab- 


228  BEET-SUGAR  MANUFACTURE. 

lishments  the  sirup  after  being  boiled  blank  was  tested  by  a  spindle. 
When  this  spindle-test  was  made  on  the  hot  sirup  it  was  unreliable 
at  the  high  density;  when  the  test  was  made  in  the  laboratory 
the  results  were  obtained  too  late  to  be  availed  of  in  making  any 
change  in  the  concentration.  An  accurate  determination  of  the 
concentration  of  the  massecuite  actually  in  the  vacuum-pan  is  the 
only  one  of  use,  and  this  can  only  be  made  by  the  boiling-control 
apparatus  already  described,  using  tables  and  temperatures  adapted 
for  sirup. 

(a)  Working  up  Centrifugal  Sirup  in  Tanks  or  Wagons. — It  is 
impossible  by  one  blank  boiling  of  a  centrifugal  sirup,  having  the 
usual  purity  of  about  75,  to  obtain  complete  crystallization  of 
sugar,  for  the  sirup  would  have  to  be  made  much  too  thick.  On 
this  account,  where  complete  sugar-extraction  is  desired,  the 
wagon-  or  tank-process  is  generally  used,  the  sirup  being  boiled 
twice,  the  first  time  not  too  stiff,  so  as  to  get  a  good  grain  and  a 
molasses  of  from  65-68  purity,  the  second  time  to  a  concentration 
suitable  for  this  purity. 

No  hard-and-fast  rules  can  be  given  for  the  boiling  of  firsts, 
because  the  density  is  dependent  on  the  size  of  grain  desired  in  the 
second  product  as  well  as  the  size  of  the  tanks  and  the  tempera- 
ture of  the  crystallizing-room.  Ordinarily  the  sirup  is  cooked 
to  a  water-content  of  13  per  cent,  and  is  put  into  rather  small  and 
shallow  tanks.  When  working  with  the  very  pure  sirups  from 
refined  sugar  the  massecuite  of  the  second  products  is  also  run 
into  tank-wagons. 

It  is  only  a  question  of  time  when  such  working  up  of  centrifugal 
sirups  from  first  products  will  disappear  from  all  factories  and  be 
replaced  by  use  of  vacuum-pans  and  crystallizers,  for  at  least 
as  good  results  as  obtained  by  the  tank-process  for  second  products 
can  be  got  with  the  poorest  boiling-apparatus  and  time  and  labor 
saved  besides.  At  least,  with  poor  apparatus  the  purity  of  the 
molasses  is  rarely  under  65,  so  that  it  is  necessary  to  boil  again 
to  a  third  massecuite,  which  must  be  crystallized  out  in  large  tanks 


AFTER-PKOnrCTS   ( »1    CKXTIUFUCJAL  SIIIUP.  229 

or  pits.  Indeed,  if  the  purity  of  this  second  product  is  only  about 
3  per  cent,  higher  than  the  final  molasses  reboiling  can  be  done 
to  advantage,  for  a  lowering  of  the  purity  one  unit  will  increase 
the  yield  of  final  product  about  1.7  per  cent,  of  the  massecuite. 

Polling  such  impure  sirups  should  be  done  with  the  aid  of  the 
boiling-control  apparatus,  using  the  following  table  calculated  for 
a  molasses  of  58  purity. 

True  purity  of  centrifugal 

sirup 68       67       66      65      64       63      62      61       60 

\Vuter-content    of    sirup 

after  boiling,  per  cent. ..   11.5  11.8  12.2  12.5  12.8  13.2  13.5  13.8  14.1 

These  values  for  the  water-content  of  thickened  centrifugal 
sirups,  it  should  be  observed,  are  the  highest  permissible  for  obtain- 
ing complete  crystallization  of  after-product  massecuites.  As  a  rule 
it  is  advisable  to  thicken  a  little  more  to  be  on  the  safe  side,  and 
make  the  water-content  2  to  1  per  cent,  less  than  given  in  the  table. 
This  is  also  advisable  for  another  reason:  If  the  massecuite  is 
too  fluid  during  separation  of  the  crystals  in  the  tank  they  sink 
to  the  bottom  while  still  very  small,  and  so  deprive  the  upper 
layers  of  the  necessary  crystal  foundation.  On  this  account  a 
certain  viscosity  is  unquestionably  necessary,  and  hence  to  obtain 
this  the  water-content  must  be  made  lower  in  proportion  to  the 
time  a  high  temperature  is  maintained  in  the  tanks.  Evidently 
boiling  should  be  somewhat  stiffer  for  large  tanks  than  for  small 
ones.  Moreover,  if  the  steaming-out  liquors  are  not  kept  separate, 
but  go 'into  the  tanks  mixed  with  the  strike,  obviously  the  thicken- 
ing must  be  greater  in  order  to  give  the  prescribed  density  to  the 
sirup  actually  in  the  tanks. 

The  initial  temperature  of  the  massecuite  i-  the  temperature 
at  time  of  discharging  the  strike,  say  80°-90°  C.  (17G°-194°  F.).  In 
order  not  to  cool  too  quickly  the  room  should  always  be  heated 
to  a  temperature  of  about  40°  C.  (104°  F.).  This  heating  is  done  by 
means  of  steam  or  heat  from  special  coke-furnaces.  In  two  months 
at  the  most  the  temperature  should  have  sunk  to  30°  C.  (86°  F.), 
and  the  crystallization  finished.  The  best-formed  crystals,  the 
size  of  which  depends  on  luck,  for  even  the  most  skillful  sugar-boiler 


230  BEET-SUGAR  MANUFACTURE. 

cannot  succeed  in  getting  massecuites  which  crystallize  uniformly, 
will  have  in  the  main  sunk  to  the  bottom,  leaving  the  supernatant 
sirup  practically  free  from  grain.  The  massecuite  can  be  removed 
without  trouble  and  purging  is  easy.  It  is  a  very  good  idea  to 
pump  the  massecuite  into  crystallizers  by  means  of  a  massecuite 
pump,  if  the  former  are  available,  and  stir  and  heat  up  to  40°- 
45°  C.  (104°-113°  F.),  or  heat  to  the  required  temperature  in  tubu- 
lar heaters  before  purging.  In  either  case  purging  can  be  done 
with  little  or  no  addition  of  dilute  molasses,  so  that  any  solution 
of  crystals  is  avoided. 

Massecuites  boiled  too  stiff,  and  consequently  improperly,  must 
be  worked  up  in  the  mixer  with  dilute  hot  molasses.  This  always 
dissolves  much  sugar,  so  that  the  purity  of  the  final  molasses  is 
often  2-3  per  cent,  higher  than  that  from  a  massecuite  properly 
boiled  and  handled. 

Tank  crystallization  is  always  unsatisfactory,  because  the  crys- 
tal foundation  soon  becomes  wanting,  as  the  crystals  in  th  >  upper 
layers  on  account  cf  their  weight  soo.i  b^gin  to  settle,  and,  conse- 
quently, the  upper  layers  of  sirup  in  the  tank  always  have  a  higher 
purity  than  those  below,  in  which  the  crystals  have  deposited.  In 
order  to  mitigate  this  evil,  stirrcrs,  either  horizontal  or  vertical, 
have  been  recommended  to  mix  the  contents  of  the  tanks,  as  well 
as  pumps  for  lifting  the  lower  layers  and  distributing  them  over 
the  surface,  so  as  to  make  the  crystals  settle  through  the  sirup 
which  is  less  exhausted.  The  cost  of  such  machinery  is,  however, 
disproportionally  great. 

Stirring  blank-boiled  massecuites  in  the  tanks  is  done  ap- 
parently most  simply  and  cheaply  by  air  bubbles,  although  this 
method  to  be  practical  requires  expensive  apparatus  and  suitable 
supervision.  This  stirring  by  compr3£sei  air  is  only  successful 
with  massecuites  of  a  purity  not  higher  than  72-73.  If  the  strike 
is  of  higher  purity,  it  must  be  allowed  to  crystallize  and  desugarizc 
some  or  be  boiled  to  grain  before  stirring.  The  tank  is  so  con- 
structed that  the  compressed  air  (inters  at  the  very  bottom, 
through  masonry  troughs  in  the  floor  for  instance.  The  air  should 
enter  in  a  rush  in  puffs,  being  under  high  pressure,  either  through 


AFTER-PRODUCTS  OF  CENTRIFUGAL  SIRUP.  231 

A  movable  pipe  or  a  hose  connected  with  the  air  line  or  through 
n  multiple  pipe  system  in  the  tank.  It  is  a  good  idea  if  these 
pipes  have  a  slit  underneath  so  that  the  compressed  air  blows  out 
sideways  and  so  stirs  the  massecuite  better.  The  time  of  tank 
crystallisation  apparently  can  be  shortened  to  some  extent,  and  a 
somewhat  better  yield  obtained  by  adding  to  the  boiled  sirup  a 
relatively  small  amount  of  fine  xuyar  crystals,  sugar-meal,  or 
powdered  sugar,  about  0. 1  per  cent,  or  less,  according  to  its  fineness. 
These  crystals  or  crystal  fragments  serve  as  a  foundation  or 
excitant  for  starting  crystallization  immediately,  and  at  least 
that  time  is  saved  which  would  have  been  necessary  for  forming 
the  initial  crystal  nuclei.  It  is  best  to  boil  the  sirup  a  little  stiffer 
for  this  manner  of  working,  so  that  the  crystals  will  remain  as 
long  as  possible  in  suspension  in  the  hot  massecuite  and  not  quickly 
settle  to  the  bottom.  As  a  rule,  the  sugar  made  in  this  way  is  of 
fine  grain,  purges  poorly  and  gives  a  poor  yield. 

That  tank-work,  in  so  many  wavs  so  disadvantageous  for 
crystallization,  gives  relatively  good  results,  is  due  to  the  fact  that 
the  time  of  graining  can  be  extended  to  any  length.  Its  disad- 
vantages are,  that  the  work  is  dirty,  expensive,  and  to  a  certain 
extent  unhealthful.  These  evils  are  the  chief  reasons  for  its 
abolishment. 

(b)  Working  up  Centrifugal  Sirup  in  Crystallizers.— By  this 
mode  of  working,  also,  the  centrifugated  sirups  of  the  first  products 
are  usually  not  desugarized  to  a  purity  of  final  molasses  at  one 
operation,  as  the  concentration  of  the  sirup  boiled  blank  would 
always  be  too  high.  For  complete  exhaustion  by  crystallization, 
centrifugal  sirups  should  be  thickened  and  boiled  as  indicated  by 
the  tables  giving  data  for  tank-work.  In  the  case  of  the  purer 
sirups,  which  must  be  as  much  supersaturated  as  possible,  far 
too  many  crystals  would  be  formed  if  crystals  were  added,  on 
account  of  the  small  crystal  nuclei  being  already  present. 

To  prevent  this,  the  purer  centrifugal  sirups,  over  70  quotient, 
should  be  boiled  thinner  than  the  table  shows;  then,  however, 
they  cannot  ever  be  reduced  to  the  purity  of  final  molassevS.  As 
a  matter  of  fact,  a  final  sirup  is  obtained  which  has  a  purity 


232  BEET-SUGAR  MANUFACTURE. 

varying,  according  to  the  sirup  boiled,  between  63  and  65  or 
higher,  so  that  such  sirup  can  be  boiled  again  to  advantage  and 
worked  up  in  tanks  or  crystallizers. 

While  it  is  true  that  purer  sirups  can  be  mixed  with  impure 
sirups,  or  molasses,  and  brought  to  a  purity  of  70-72,  and  that 
such  mixtures  can  easily  bo  boiled  and  brought  down  to  a 
molasses  purity,  the  crystallization  is  injured  by  such  methods 
and  the  greatly  increased  volume  of  the.  massecuite  requires 
more  crystallizer  capacity  and  more  labor  for  purging. 

Ordinarily,  centrifugal  sirups  are  boiled  for  crystallizer  work 
to  a  water-content  of  about  10  per  cent,  and  crystals  are  allowed 
to  form  by  cooling  in  the  crystallizer,  or  15-20  per  cent,  of  sugar 
is  added  as  a  foundation.  The  sugar  added  should  always  be  first 
warmed  and  mixed  with  hot,  thick  sirup,  as  addition  of  cold 
sugar  might  form  second  grain.  It  is  much  better  to  draw  the 
sugar  slowly  into  the  vacuum-pan  after  the  sirup  has  become 
suitably  concentrated,  either  directly  or  mixed  with  sirup. 

Another  method  of  boiling  consists  in  thickening  the  sirup, 
which  should  not  have  a  purity  greater  than  72,  at  the  high  tem- 
perature of  95-100°  (203-212°  F.)  to  a  water-content  of  7-9  per 
cent:  and  then  induce  crystallization  by  shaking  violently  by 
means  of  steam  injection.  A  comparatively  large  quantity  of 
fine  crystals  are  formed  by  this  action,  which  accelerates  graining, 
and  providing  they  attain  sufficient  size,  do  not  clogthe  centrifugals. 

Cooling-off  in  crystallizers  must  take  place  very  slqwly.  Such 
apparatus  should  be  equipped  with  a  water-jacket,  so  that  the 
massecuite  can  be  warmed  when  necessary.  The  final  tempera- 
ture should  not  be  too  low,  usually  not  lower  than  40°  (104°  F.). 
At  times  hot  or  cold  air  is  passed  over  the  massecuite,  which 
regulates  the  cooling,  and  at  the  same  time  causes  evaporation 
and  a  further  concentration. 

Massecuite  in  crystallizers  only  needs  to  be  stirred  very  slowly, 
at  most,  the  stirrer  should  make  from  one  to  two  revolutions  per 
minute,  and  may  even  be  discontinued  for  certain  periods. 
When  warming  or  cooling,  obviously  the  stirrer  must  be  con- 
stantly in  motion. 


AFTER-PRODUCTS  OF  CENTRIFUGAL  SIRUP.  L^o 

The  stirring  period  depends  on  the  extent  the  sugar  is  to  be 
extracted,  and  upon  the  purity  of  the  resulting  sirup.  Two  to 
three  days  are  sufficient  to  reduce  a  sirup  of  75  purity  to  one  of 
65  purity.  Five  to  six  days  at  least  are  necessary  to  reduce  a 
sirup  of  65-70  purity  to  about  60  purity.  It  is  no  more  possible 
by  this  process  than  by  tank-work  to  reduce  sirups  of  higher  purity 
than  70  in  a  single  boiling  to  the  purity  of  true  molasses.  More- 
over, the  impure  sirups  never  crystallize  uniformly;  often  the 
purity  of  the  centrifugated  molasses  shows  large  variation,  and 
the  purging  itself  is  frequently  very  difficult. 

When  crystallization  is  complete,  the  massecuite  should  usually 
be  thinned  to  a  more  or  less  degree  so  as  to  make  it  purge  easily, 
Cooling  on  the  way  to  the  centrifugals  must  be  avoided. 

If  sugar  is  added  for  grain  foundation,  raw  first  sugars 
should  be  used  to  get  good,  large  crystals.  Usually,  however,  fine- 
grained after-product  sugar  is  used,  or  a  part  of  the  massecuite 
of  the  previous  crystallizer  is  put  in.  Working  thus  simplifies 
the  process,  it  is  true,  but  second  grain  is  always  formed  in  with 
the  large  crystals,  while  the  latter  tend  to  form  in  relates,  which 
are  not  so  much  desired  and  arc  apt  to  purge  badly.  Broken 
crystals  are  recommended  for  rapid  crystallization.  Crystal 
fragments  and  splinters  remove  sugar  from  solution  with  great 
energy  and  grow  into  normal  crystals,  after  which  they  behave 
like  any  other  crystal. 

(c)  Boiling  Centrifugal  Sirups  to  Grain. — The  difficulty  en- 
countered in  completely  desugarizing  sirups  of  high  purity  in 
crystallizers  can  be  overcome  by  boiling  such  sirups  in  the  vacuum- 
pan,  either  to  grain  or  with  grain  previously  added.  If  centrifugal 
sirups  are  grained,  or  grain  added  to  the  weakly  supersaturated 
sirup,  sufficient  sugar  can  be  crystallized  out  by  one  proper  boiling 
in  a  vacuum-pan  to  reduce  the  purity  of  the  sirup  to  at  least  65-67. 

With  no  fear  of  trouble,  the  concentration  of  such  impure  sirup 
can  be  made  so  high  that  any  further  crystallization,  up  to  com- 
plete desugarizing  of  the  molasses,  can  be  accomplished  either  by 
reboiling  in  the  vacuum-pan  itself,  at  the  pan  temperature,  or  in 
crystallizers  by  gradual  cooling.  In  boiling  centrifugal  sirups  to 


234  BEET-SUGAR  MANUFACTURE. 

grain,  just  as  in  boiling  juice-sirups,  the  pan  must  be  regulated  so 
that  the  mother-sirup  is  kept  continually  at  the  proper  degree 
of  supersaturation  during  evaporation,  and  not  obtained  by 
gradual  cooling,  as  in  regular  crystallizer  work,  where  crystalliza- 
tion must  perforce  take  place  at  a  lower  temperature,  not  so 
favorable  for  the  purer  sirups. 

There  are  many  different  and  conflicting  ideas  about  boiling 
sirups  to  grain.  Those  methods  emphasizing  details  of  minor  im- 
portance as  far  as  the  actual  conditions  affecting  crystallization 
are  concerned,  such  as,  for  example,  the  kind  of  mechanical  stirrer 
to  use  or  the  arrangement  of  the  sirup  feed-pipe,  obviously  will  not 
lead  to  results  of  permanent  value.  The  only  satisfactory  boiling 
method  is  one  which  keeps  the  sirup,  at  every  stage  of  the  process, 
at  a  concentration  most  favorable  for  crystallization,  and  in  which, 
by  the  aid  of  suitable  circulating  devices,  the  temperature  is  con- 
tinually uniform  throughout,  and  gives  a  boiling-point  actually 
corresponding  to  the  vacuum. 

Whereas,  in  boiling  juice-sirups  to  grain,  maintenance  of  proper 
concentration,  according  to  external  appearances,  can  be  learned 
after  some  practice,  and  mistakes  made  here  might  be  corrected 
in  working  up  after-products,  in  the  case  of  centrifugal  sirups 
unexpected  difficulties  are  met  owing  to  their  great  viscosity,  which 
is  affected  by  temperature.  Final  boiling  of  centrifugal  sirups, 
however,  has  to  be  done  practically  perfectly,  to  avoid  large  losses 
in  the  sugar-yield.  In  this  work  the  boiling-control  apparatus  is 
again  of  service,  since  the  boiling  must  be  slow,  and  therefore  the 
indications  of  the  simplest  form  of  apparatus  can  be  followed  with- 
out trouble;  such  apparatus  is  quite  necessary  for  the  boiling  to 
grain,  and  should  show  the  water-content  of  the  sirup. 

The  concentration  of  the  sirup,  or  mother-liquor,  that  is,  its 
water-content,  must  be  calculated  for  every  boiling,  especially  for 
the  various  pure  sirups.  In  these  calculations,  too,  the  super- 
saturation-coefficients  are  the  fundamental  data. 

While  graining,  the  coefficient  for  the  better  grade  cen- 
trifugal sirups  should  be  the  same  as  for  j  uice-sirups,  but  be  taken 
somewhat  greater  when  the  purity  falls  as  low  as  68. 


AFTER-PRODUCTS   OF  (  EXTRILUGAL  SIRUP.  235 

After  grain  has  been  formed,  the  coefficient,  just  after 
feeding  with  sirup,  should  be  somewhat  diminished;  but  as  soon 
as  the  crystals  become  of  perceptible  size  it  should  again  be 
raised,  but  raised  gradually,  according  as  the  crystals  grow  and 
the  purity  lowers.  It  is  advisable  to  lower  it  again  and  when  the 
pan  is  finished. 

In  actual  practice,  data  of  supersaturation-coefficients  are  not 
of  use  by  themselves,  but  the  water-content  of  sirups  of  various 
purities  and  at  different  times  should  be  calculated  by  means  of 
such  tables;  for,  with  help  of  such  data  and  by  use  of  the  control- 
apparatus,  the  sugar-boiler  can  finally  make  the  boiling  a  purely 
mechanical  process. 

Grain  can  be  made  from  centrifugal  sirup,  thickened  accord- 
ing; to  the  indications  of  such  tables,  or  by  the  string-proof,  or, 
as  in  the  juice-sirups,  by  introduction  of  new  liquor,  or  even 
solely  by  agitation  caused  by  mechanical  stirrers,  this  being 
simply  what  is  known  as  crystallization  in  movement,  and  is 
regulated,  according  to  the  data  of  the  tables,  so  that  in  a  certain 
time  the  proper  amount  of  crystals  is  formed  at  the 'prescribed 
concentration.  Special  skill  is  not  necessary  for  making  grain  by 
this  latter  process;  the  pan-man  must  rather  avoid  allowing 
grain  to  form  too  long.  In  the  purer  sirups,  of,  say,  75  quotient  or 
more,  suitable  grain  is  formed  in  a  few  minutes  after  the  concen- 
tration is  reached.  In  more  impure  sirups,  J— J  an  hour  or  more 
passes  before  the  grain  becomes  visible.  Obviously,  graining  can 
be  expedited  by  using  greater  concentrations;  but,  if  that  is 
done,  there  are  always  too  many  crystals  and  the  grain  is  too 
fine.  As  in  the  case  of  first  product,  it  is  important  that  the 
charging  sirup  is  properly  heated  so  that  any  sugar  which  has 
separated  out  in  cooling  after  the  centrifugal  work  or  passed 
through  the  sieves  will  be  redissolved.  If  this  is  neglected,  there 
will  be  fine  grain  in  the  pan  which  will  interfere  with  the  regularity 
of  the  graining. 

Diluting  the  sirup,  which  is  sometimes  recommended,  is  entirely 
unnecessary.  It  increases  cost  of  evaporation  and  lengthens  boiling. 
It  is  only  needed  when  very  large  grains  have  been  left  in  the  sirup. 


236  BEET-SUGAR  MANUFACTURE. 

i 

As  soon  as  suitable  grain  is  formed,  sirup  is  again  drawn  in, 
and  the  steam  in  the  coils,  which  was  entirely  shut  off  during 
forming  of  the  grain,  is  again  applied,  and  the  heating  and  juice- 
feed  so  regulated  that  the  water-content  remains  constantly  at 
the  value  calculated  for  this  particular  strike.  Boiling  must  go 
slower  in  proportion  to  the  extent  that  crystallization  is  to  be 
carried  in  the  vacuum-pan.  In  16-24  hours,  ordinarily,  a  sirup 
purity  of  about  68  is  reached,  but  for  62  the  boiling  must  last 
60-72  hours. 

It  does  not  appear  advisable  to  carry  this  desugarizing  of  the 
mother-sirup  in  vacuum-pans  to  more  than  65-68  purity.  The 
massecuite,  when  boiled  to  about  this  point,  is  discharged  into 
crystallizers,  in  which  it  is  stirred  for  several  days,  while  it  is 
gradually  cooled  and  a  regulated  amount  of  water  added. 
Cooling  is  so  regulated  that  the  temperature  sinks  about  10° 
(18°  F.)  in  24  hours,  experience  having  shown  that  crystallization 
of  the  sugar  on  a  crystal  foundation  progresses  most  favorably 
under  such  conditions. 

The  supersaturation  increases  as  the  temperature  falls,  although 
sugar  is  continually  crystallizing  out.  The  reason  is  chiefly  because 
the  saturation-coefficient,  as  has  been  explained  before,  decreases 
with  falling  temperature.  The  supersaturation  will,  therefore,  be 
so  great  that  finally  second  grain  will  begin  to  form.  In  order  to 
prevent  this  second  grain  forming  in  the  crystallizers,  since,  being 
in  the  form  of  crystal  flour,  it  cannot  be  removed  by  the  centrifugals 
and  makes  the  purging  very  bad,  water  is  added  at  a  prescribed 
temperature,  the  amount  being  proportioned  according  to  the 
purity  of  the  massecuite  and  the  water-content  of  the  mother- 
sirup  at  the  time  of  discharging  the  pan. 

For  example,  on  the  first  day  the  temperature  of  the  jacket 
of  the  free  space  of  crystallizers  should  drop  from  90°  to  75° 
(194°  F.  to  167°  F.)  on  the  second  day  to  65°  (149°  F.),  on  the 
third,  55°  (131°  F.),  on  the  fourth,  45°  (113°  F.).  Water  in  cal- 
culated amount  should  be  added  for  every  4-5°  (7-9°  F.)  drop 
starting  from  80°  (176°  F.)  (condensed  water  of  best  quality 
being  used).  As  a  basis  for  this  calculation,  experience  shows 


AFTER-PRODUCTS   OF  CENTRIFUGAL  SIRUP.  237 

that  crystallization  progresses  best  without  formation  of  new 
grain  at  a  supersaturation  of  1.05-1.15.  When  the  massecuite 
is  properly  boiled,  for  every  temperature  drop  of  4-5°,  4  liters 
of  water  are  added  per  cubic  meter  of  crystallizer  capacity  (0.03 
gallon  per  cubic  foot)  for  70  purity,  3.5  liters  (0.026  gallon), 
for  75  purity,  and  2  liters  (0.015  gallon)  for  80  purity.  By  this 
process,  in  the  space  of  4-5  days  there  will  be  a  massecuite 
cooled  to  35°-45°  C.  (95°-113°  F.),  which  will  be  free  from 
gumminess  and  purge  easily,  giving  an  after-product  sugar  of 
good  grain  and  high  purity,  as  well  as  a  true  molasses. 

In  order  to  arrive  at  these  results  with  certainty  it  is  advis- 
able to  make  systematic  tests  of  the  mother  liquor  separated 
from  the  crystals  at  periods  of  two  and  four  days'  stirring,  taking 
the  apparent  dry  substance  (Brix)  according  to  the  dilution 
method  and  the  apparent  purity.  At  the  end  of  two  days  the 
water  content  should  be  12  per  cent.,  corresponding  to  91°  Brix, 
in  a  syrup  of  apparent  purity,  62-64, -and  after  four  days,  15-16 
per  cent,  water,  corresponding  to  88-89  Brix.  It  is  worthy  of 
special  note  that  the  apparent  purity  differs  from  the  true  the 
more  the  sirup  or  molasses  is  diluted  for  the  Brix  determination 
and  the  lower  the  ratio  of  ash  to  organic  non-sugar.  This  differ- 
ence is  proportionally  much  greater  as  the  purity  lowers. 

In  boiling  centrifugal  sirups,  mechanical  sugar  losses,  such  as 
foaming  and  entrainment,  are  more  likely  to  occur  than  when 
boiling  juice-sirups,  because  the  former  are  more  viscous  and 
become  superheated  more  readily,  especially  if  there  is  trouble 
with  the  vacuum,  but  by  some  care,  and  having  a  suitable  vapor- 
space,  loss  can  always  be  avoided. 

Losses  from  decomposition  of  sugar  will  take  place  in  boiling 
and  heating  centrifugal  sirups,  as  it  does  in  every  sugar-solution. 
It  is,  however,  very  small  in  alkaline  sirups;  and  in  the  newer  after- 
product  processes  it  is  less  than  in  tank-work,  because,  as  has  been 
shown  above,  long-continued  heat  has  a  more  injurious  influence 
than  a  higher  temperature  maintained  for  a  shorter  time,  providing 
that  this  does  not  exceed.  90°-100°  C.  (194°-212°  F.).  There  is  a 
marked  sugar  decomposition  in  neutral  or  acid  sirups,  however. 


238  BEET-SUGAR  MANUFACTURE. 

The  treatment  of  after-product  sugars  is  therefore  precisely  the 
same  as  for  the  first,  as  far  as  this  latter  point  is  concerned. 

In  many  factories,  after-products,  especially  those  which  are 
fine-grained,  of  low  yield,  and  practically  unsalable,  are  redissolved 
in  the  thin  juice.  Sometimes  these  massecuites  are  boiled  up  and 
discharged  into  tanks  with  sieve  bottoms  and  not  centrifugated, 
the  mother-sirup  being  drained  off  after  crystallization,  and  the 
slimy  sugar  remaining  behind  melted  up  in  the  same  tank.  Since 
every  boiling  entails  loss  and  expense,  it  is  advisable  to  calculate 
for  each  individual  lot  whether  there  is  any  profit  in  working  over 
for  after-products.  The  general  idea  is  that  molasses  sugars  are 
better  in  proportion  as  the  sirup  is  less  completely  desugarized, 
so  that  a  product  giving  a  molasses  of  63  purity  must  be  better 
than  one  giving  60  purity.  This  is  erroneous.  The  quality  of 
after-products  depends  principally,  as  does  that  of  first-products, 
on  the  juice  treatment  and  the  graining.  If  these  processes  are 
carried  out  carelessly  it  certainly  will  be  necessary  to  shorten  the 
crystallization  period  to  obtain  massecuites  which  will  purge  well 
and  avoid  slimy  sugars.  With  good  crystallization  the  grains 
are  well  formed  and  the  sugar  granular  and  not  slimy,  and  the 
yield  88  or  over.  The  better  class  after-products  usually  bring 
such  a  good  price  that  they  are  more  profitable  to  sell  at  once, 
except  in  particular  cases,  as,  for  example,  when  it  is  desired  to  sell 
the  product  from  the  factory  directly  to  the  consumer. 

The  better  class  of  after-products  of  this  class  can  be  made  by 
a  special  "  covering  process,"  if  they  are  too  fine-grained  and  have 
a  very  viscous  mother-sirup,  and  so  give,  by  ordinary  purging,  a 
slimy  sugar  of  low  polarization.  By  this  process,  molasses  or  sirup 
from  a  previous  purging  is  run  simultaneously  with  the  massecuite 
into  the  drum  of  the  centrifugal  after  it  is  already  in  motion,  this 
sirup  being  of  the  same  purity  as  that  of  the  mother-sirup  of  the 
massecuite.  This  cover-sirup  is  so  far  diluted  that  it  is  only 
saturated,  or  even  unsaturated,  and  is  heated  more  or  less.  Usually 
a  molasses  of  70°-75°  Brix  (38°-41°  Be.)  is  used  and  warmed  up  to 
50°-70°  C.  (122°-158°F.).  By  this  means,  most  of  the  viscous 
mother-sirup  of  the  massecuite  is  washed  or  forced  out  by  the  more 


AFTER-PRODUCTS  OF  CENTRII  UCIAL  SIRUP.  239 

mobile  cover-molasses  as  soon  as  the  massecuite  gets  on  the  sieve. 
Washing  and  purging  is  made  possible  and  is  very  thorough,  because 
of  the  cover-molasses  acting  only  on  very  thin  films  of  unpurged 
massecuite,  while,  on  the  contrary,  the  ordinary  cover-sirup  method 
gives  only  unsatisfactory  purging,  as  the  sirup  acts  on  a  very 
irresistant  layer,  as  the  centrifugal  is  full  before  the  sirup  is  applied. 
As  the  whole  operation  is  complete  in  the  minimum  time,  the 
dilute  molasses  has  no  time  to  dissolve  the  grain,  and  only  dilutes 
the  sirup  enveloping  the  crystals  which  will  not  purge.  In  this 
way  a  sugar  is  obtained  which  is  light,  easily  conveyed,  and  of 
high  yield,  and  a  molasses  with  the  same  purity  as  that  of  the 
mother-sirup. 


CHAPTER  XXI. 
THE  PURIFICATION  OF  CENTRIFUGAL  SIRUP. 

BEFORE  boiling  down  for  the  manufacture  of  " seconds,"  the 
different  sirups  that  have  drained  off  are  frequently  subjected  to 
a  purification  process.  The  simplest  treatment  is,  in  case  they  have 
a  too  high  alkalinity,  a  saturation  with  carbonic  or  sulphurous 
acid  gases.  If,  however;  the  sirups  are  saturated  to  an  alkalinity 
of  from,  say,  0.02  to  0.04,  and  the  massecuites  of  the  No.  1  product, 
in  consequence,  show  alkalinity  of  about  0.05,  the  alkalinity  of  the 
sirup  coming  from  them  is  not  more  than  0.05  to  0.10.  An  alka- 
linity of  at  least  0.05  is  not  only  harmless,  but  is  even  absolutely 
necessary,  if  sirups  are  to  be  kept  alkaline  during  the  long  period 
of  crystallization  in  the  tanks,  or  during  the  days  of  boiling  down 
or  crystallizing  in  the  crystallizers.  Consequently,  carbonatation 
of  sirups  in  normal  process  is  not  necessary  and  can  be  omitted, 
especially  as  the  sirups  are  diluted  thereby  and  the  subsequent 
expense  of  evaporating  them  is  increased. 

Filtration  of  sirup  before  the  boiling  is  frequently  regarded  as 
advantageous,  because  these  sirups  are  always  more  or  less  turbid, 
owing  to  some  precipitation  which  takes  place  during  the  first 
boiling.  Since  the  weight  of  these  precipitates,  which  consist 
chiefly  of  organic  calcium  and  iron  salts  (oxalates),  is,  however, 
extremely  slight  (only  0.01  to  0.1  per  cent.),  and  as,  even  when  the 
sirups  are  dilute,  it  is  difficult  to  make  them  filterable  by  addition 
of  porous  substances,  it  is  obvious  that  the  uses  and  practicability 
of  filtration  are  extremely  questionable. 

It  has,  in  fact,  never  been  proven  that  there  is  an  increase  in 

240 


THE  PURIFICATION   ol    <  KXTRIFUGAL  SIRUP.  241 

purity  of  sirups  from  this  operation,  although,  indeed,  it  is  asserted 
that  the  physical  properties  are  improved  by  nitration  preceded 
by  a  saturation  with  sulphurous  acid,  but  proof  of  this  assertion 
is  likewise  lacking. 

On  the  other  hand,  the  fact  has  been  established  in  practice 
that  normal  sirups  can  be  worked  up  to  advantage,  and  give  thor- 
oughly satisfactory  results,  without  any  nitration  or  saturation 
with  gas. 

Another  method  of  purifying  sirup  consists  in  treating  hot, 
dilute  sirup  with  lime  (or  baryta),  and  subsequent  saturation 
with  carbonic  or  sulphurous  acid.  Since  lime  here  acts  upon  the 
non-sugars,  which  are  present  to  a  considerable  extent,  just  as  it 
does  upon  the  original  thin  juices,  it  is  clear  that  a  perceptible 
improvement  can  be  attained  by  this  method  only  when  the  orig- 
inal defecation  was  not  sufficiently  complete,  or  was  conducted 
at  too  low  a  temperature.  It  has  never  been  found  that  the  purity 
of  the  sirup  is  increased  by  the  action  of  lime,  but,  on  the  other 
hand,  it  is  said  that  after  this  treatment  the  sirups  are  more  readily 
crystallizable,  an  advantage  which,  if  it  is  actually  realized,  is 
partly  traceable  to  the  dilution,  since  it  is  easier  to  boil  dilute 
sirups  than  concentrated  ones,  where  there  is  no  control  used.  It 
is  seldom  that  the  unpleasantness  of  such  a  further  saturation 
process,  and  the  cost  of  carrying  it  out,  will  be  covered  by  increase 
in  sugar-yield. 

If  the  diffuser-juice  has  been  insufficiently  treated  with  lime, 
an  extremely  troublesome  and  wasteful  phenomenon  may  take 
place.  This  is  the  so-called  froth  fermentation  of  the  second 
massecuites.  This  makes  itself  evident  by  the  massecuites  begin- 
ning to  rise  after  they  are  placed  in  the  vats  or  crystallizers. 
Throughout  the  mass,  a  number  of  tiny  gas  bubbles  are  formed, 
which  cannot  escape  on  account  of  the  viscosity,  and  hence  grad- 
ually raise  up  the  massecuite  until  the  whole  of  it,  or,  at  any  rate, 
the  greater  part  of  the  upper  portion,  becomes  frothy.  Of  course, 
the  volume  of  the  mass  is  increased  to  the  amount  of  the  volume  of 
the  gas  produced,  and,  as  a  result,  it  runs  over  the  tops  of  the  tanks. 
The  evolution  of  gas  is  greatest  while  the  massecuites  are  still  hot; 


242  BEET-SUGAR   MANUFACTURE. 

it  diminishes  as  they  cool  off,  ceases  altogether  at  60°  (140°  F.). 
The  amount  of  gas  produced  varies  greatly ;  sometimes  only  a  slight 
foamy  layer  is  formed,  while  in  other  cases  the  space  occupied  by 
the  gas  amounts  to  from  50  to  100  per  cent,  of  that  occupied  by  the 
massecuite  itself. 

The  gas  evolved  consists,  either  entirely  or  for  the  greater  part, 
of  carbon  dioxide.  The  cause  of  this  generation  of  carbonic  acid 
is  not  fermentation,  although  it  is  so  named  on  account  of  the 
fact  that,  as  far  as  outer  appearance  goes,  it  would  seem  to  be  such; 
the  fact  that  the  phenomenon  is  strongest  at  temperatures  above 
80°  C.  (176°  F.)  shows  very  clearly  that  it  is  not  a  fermentation, 
because,  at  such  high  temperatures,  any  micro-organism  capable  of 
producing  fermentation  would  be  either  killed  outright  or,  at  least, 
show  a  diminished  activity.  The  real  cause  is  to  be  sought  rather 
in  the  chemical  decomposition  of  certain  organic  non-sugars; 
probably  they  are  decomposition  products  of  invert-sugar,  and 
other  organic  substances  of  high  molecular  weight  which  get  into 
the  juices  during  working-up  of  poor  beets,  particularly  those  which 
have  been  frozen  or  are  decayed.  Such  compounds  may  not  have 
been  completely  decomposed  in  the  defecation,  on  account  of 
defecating  too  cold,  or  for  too  short  a  time.  After  these  unstable 
compounds  have  collected  in  the  sirups  and  are  exposed  to  high 
temperature  for  a  considerable  length  of  time,  they  begin  to  de- 
compose, and  particularly  when  the  sirups  have  absorbed  oxygen 
from  the  air  during  centrifugation.  One  of  the  decomposition- 
products  is  carbonic  acid,  while  the  other  products  are,  in  the 
main,  not  volatile,  being  in  fact,  for  the  greater  part,  non-volatile 
organic  acids,  which  latter  diminish  the  alkalinity  of  the  sirup, 
or  even  give  it  an  acid  reaction.  If  such  sirups  contain  nitrites, 
as  is  sometimes  the  case,  the  latter  will  be  decomposed  by  the 
organic  acids,  and  nitric  oxide  will  be  set  free  with  the  carbon 
dioxide.  Dark-colored  substances  are  likewise  formed  which  im- 
part a  dark-brown  color  to  the  whole  of  the  massecuite,  as  well 
as  to  the  sugar  prepared  from  it.  The  formation  of  foam,  further- 
more, is  in  proportion  to  the  number  of  times  the  sirup  is  boiled, 
and  is,  therefore,  more  likely  to  take  place  in  the  manufacture  of 
the  third  product  than  with  the  seconds. 


THE  PURIFICATION  OF  CENTRIFUGAL  SIRUP  243 

The  sugar-yield  in  such  cases  will,  as  a  matter  of  fact,  not  be 
greatly  affected,  but  the  product  is  dark-colored,  of  a  fine  grain, 
is  neutral  or  acid  in  reaction,  and  usually  contains  invert-sugar, 
so  that  it  does  not  keep  as  well  and  is  of  less  value;  the  same 
being  true  of  the  molasses  produced,  which  likewise  contains  invert- 
sugar  and  is  neutral  or  acid. 

To  prevent  foam-fermentation,  a  vigorous  treatment  of  diffuser 
or  thin  juice  with  lime  in  the  defecation  is  to  be  recommended 
and  is  usually  effective.  Those  sirups  showing  a  tendency  this  way 
should  be  boiled  under  as  high  a  vacuum  as  possible,  at  a  low 
temperature,  and  in  some  cases  with  the  addition  of  soda.  If 
these  agents  do  not  help  sufficiently,  the  above-mentioned  treat- 
ment of  the  sirup  with  lime  will  surely  be  of  some  use. 

As  in  the  case  of  the  juices,  many  other  purification  processes 
have  been  proposed  for  sirups  in  which  chemicals,  such  as  baryta 
or  barium  salts,  hydrosulphurous  acid,  ozone,  or  the  electric  cur- 
rent, etc.,  are  said  to  precipitate  the  non-sugars.  Xo  practical 
results  have  yet  been  obtained  in  this  way,  and,  so  long  as  it  is 
not  proven  that  by  these  agents  it  is  possible  to  crystallize  sugar 
from  an  actual  molasses,  it  may  be  said  that  they  have  absolutely 
no  practical  significance. 

Many  like  to  carry  the  sirups  from  the  firsts,  or  part  of  them, 
back  to  some  previous  stage  of  process,  putting  it,  for  example,  in 
the  diffusion  battery,  in  the  raw  juice,  in  the  defecation,  or  in  the 
thin  juice.  As  a  matter  of  fact,  there  is  an  increase  in  the  yield  of 
"  firsts,"  when  the  process  is  conducted  in  this  way,  if  the  yield  is 
compared  with  that  obtained  when  the  massecuite  is  not  boiled 
with  sirup.  The  carrying-back  of  the  sirups  into  the  juices  then 
acts  favorably  upon  the  boiling,  particularly  with  the  juices  and 
sirups  of  high  purity,  in  so  far  as  the  duration  of  the  process  is 
lengthened,  because  the  mixed  juices  have  a  lesser  purity.  If,  for 
example,  an  amount  of  sirup  of  78°  purity,  equivalent  to  3  per  cent, 
of  the  weight  of  the  beets,  is  introduced  into  juice  of  94°  purity,  the 
resulting  mixture  will  then  have  a  purity  of  91 .5°.  Slow  boiling  in- 
creases the  yield  of  firsts,  as  we  have  alreadj'  seen.  This  increased 
sugar-yield  is  obtained  in  a  much  more  simple  manner  when  the 


244  BEET-SUGAR  MANUFACTURE. 

sirups  are  not  introduced  into  the  juices  until  after  the  com- 
pletion of  a  slow  boiling  of  the  pure  juice  in  the  vacuum-pan.  After 
its  introduction,  the  massecuite  is  boiled  again  for  a  considerable 
length  of  time.  This  last  procedure  is  always  applicable,  while  the 
former  method  can  be  carried  out  to  advantage  only  when  the 
juices  are  very  pure,  for  otherwise  a  bad  grain  results,  and  the  sugar- 
product  has  essentially  poorer  properties.  It  has  not  been  proven 
that  there  is  purification  of  the  sirup  by  defecation  and  carbonata- 
tion  when  it  is  introduced  into  the  raw  juices,  although  it  has  been 
frequently  claimed  that  this  is  the  case;  in  fact,  no  satisfactory 
explanation  can  be  given  why  this  should  be  so,  for  it  is  not  easy 
to  see  how  non-sugars  in  the  sirup  can  be  precipitated  or  changed 
by  a  repetition  of  the  defecation  when  they  have  already  under- 
gone such  a  treatment  in  the  thin  juice  under  exactly  identical 
conditions. 


CHAPTER  XXII. 
MOLASSES  AND  ITS  UTILIZATION. 

BY  molasses  is  understood,  in  the  practical  sense,  that  final 
product  in  the  manufacture  of  sugar  from  which,  by  maintaining 
all  those  conditions  favorable  for  a  crystallization,  no  more  sugar 
can  be  obtained. 

The  theoretical  explanation  of  the  inability  of  the  sugar  to 
crystallize  out  from  the  molasses  lies  in  the  fact  that  in  it  the 
sugar  remains  dissolved  in  the  non-sugars,  and,  conversely,  at 
all  concentrations,  the  non-sugars  are  held  in  solution  by  the  sugars. 

It  is,  to  be  sure,  also  possible  that  the  cause  of  a  non-crystalli- 
zation may  be  due  to  the  viscosity  being  very  great.  In  such 
cases,  however,  this  viscosity  is  caused  by  too  great  supersaturation 
of  the  sirup,  or  by  too  low  temperatures;  and  it  can  be  avoided 
by  a  properly-conducted  thickening  process  in  the  pan,  or  by  the 
use  of  high  temperatures,  but  in  such  cases  the  sirup  is  not  a  mo- 
lasses in  the  sense  of  the  definition  given  above. 

The  lowest  purity  which  has  been  found  in  the  molasses  from  a 
beet-sugar  factory  is  '54°  to  55°  (equivalent  to  51°  to  52°  apparent) . 
On  an  average,  where  the  work  is  conducted  carefully,  the  purity  of 
the  molasses  is  from  58°  to  60°,  while  in  many  factories  it  is  60° 
or  higher.  It  appears  that  molasses  products  of  higher  purity 
are  obtained  from  the  purer  sirups.  When  the  purity  of  the  sirup 
is  less  than  91°  to  92°,  molasses  under  60°  is  usually  obtained, 
particularly  when  it  contains  organic  lime-salts  as  a  result  of  a 
vigorous  defecation,  for  the  latter  diminish  the  solubility  of  the 
sugar.  Again,  the  molasses  obtained  at  the  beginning  of  a  cam- 
paign, or  from  the  juices  first  obtained,  usually  is  less  pure  than 

245 


246  BEET-SUGAR  MANUFACTURE. 

that  at  the  end  of  the  campaign.  It  is  evident  from  this  that 
the  nature  of  the  non-sugars  present  plays  a  not  unimportant  part 
with  reference  to  the  formation  of  molasses. 

Most  of  the  molasses  of  commerce  is  not  molasses  in  the  strict 
sense  of  the  word.  It  may  either  contain  crystallizable  sugar, 
because  the  last  crystallization  process  has  been  poorly  conducted, 
when  the  removal  of  sugar  from  the  mother-syrup  is  incomplete, 
or  it  may  be  due  to  the  fact  that,  during  centrifugation,  sugar  was 
dissolved  by  use  of  too  much  water  or  steam. 

The  composition  of  a  molasses  of  60°  purity,  as  ^t  occurs  sur- 
rounding the  crystals  in  a  completely  crystallized  massecuite,  as 
far  as  the  water  and  sugar-content  are  concerned,  has  already 
been  given.  In  the  condition  in  which  it  is  thrown  off  in  centrif- 
ugation, when  the  work  has  been  properly  conducted,  it  contains, 
according  to  the  temperature  prevailing  at  the  end  of  the  crystal- 
lization, from  13  to  15  per  cent,  of  water.  Such  a  molasses, 
however,  is  not  marketable,  because  it  is  so  viscous  at  ordinary 
temperatures  that  it  can  be  neither  pumped  up  nor  filled  into 
barrels.  It  must,  therefore,  be  diluted  until  the  water-content 
corresponds  to  about  18  to  20  per  cent.,  or  to  a  density  of  81°  to 
83°  Brix  (43.5°-44.5°  Be.),  and  ordinarily  this  is  done  immediately 
after  centrifugation  by  warming  it  in  collecting-tanks  by  direct 
steam-injection.  After  the  molasses  has  been  heated  and  diluted 
in  this  way,  it  can  be  pumped  readily  by  ordinary  sirup-pumps. 
Molasses  which  has  been  stored  in  vats  or  pits  till  it  assumes  the 
ordinary  temperatures  cannot  be  handled  by  ordinary  pumps  even 
when  its  density  is  only  80°  Brix  (43°  Be.) ;  in  such  cases  it  is 
raised  either  by  means  of  a  chain  pump,  or  by  one  such  as  is  made 
for  pumping  massecuite. 

The  molasses  leaves  the  factory  in  barrels  or  in  tank-wagons. 
It  may  be  worked  up  into  sugar,  made  into  cattle-fodder,  or  used 
for  the  manufacture  of  alcohol,  and  for  certain  other  purposes 
which  do  no  not  interest  us  here. 

There  were  formerly  quite  a  number  of  different  processes  used 
for  obtaining  sugar  from  molasses,  of  which  all  those  using  alcohol 
as  a  solvent,  or  that  were  otherwise  expensive,  disappeared  with  the 


MOLASSES  AND  ITS  UTILIZATION.  247 

dropping  of  sugar  prices.  To-day  there  is,  with  the  exception  of 
the  strontia  method,  which  is  only  used  in  sugar-refineries  and  not 
at  all  in  beet-root  factories,  no  method  of  practical  importance 
other  than  those  of  osmosis  and  precipitation. 

Osmosis  depends  upon  the  fact  that  the  different  components 
of  the  molasses  possess  a  very  different  diffusion  capacity.  Since 
not  alone  the  non-sugars,  but  also  the  sugar  itself,  is  diffusible,  it  is 
evident  that  osmosis  can  only  effect  the  separation  of  the  molasses 
into  a  sirup  of  high  purity,  and  into  the  so-called  osmosis-water, 
which  is  a  sugar-solution  of  less  purity  than  the  molasses  itself. 
The  action  of  osmosis  is  more  or  less  satisfactory,  according  to  the 
nature  of  the  non-sugars  present  in  the  molasses  (or  rather  in  the 
low-grade  sirup,  for  molasses  itself  can  be  seldom  subjected  to 
osmosis  with  advantage).  Inasmuch  as  the  salts  of  the  alkalies 
diffuse  most  readily,  it  follows  that  sirups  with  a  high  ash  can  be 
improved  by  osmosis.  Consequently  the  efficiency  of  osmosis 
differs  not  only  in  different  factories,  but  in  the  same  factory  in 
different  years.  Some  sirups  will  not  give  good  results  even  when 
but  one  osmosis  is  attempted,  while  others  can  be  subjected  to  the 
process  twice  in  succession.  Naturally,  however,  the  second  time 
will  never  give  as  favorable  results  as  the  first,  for  the  reason  that 
those  parts  of  the  sirup  which  diffuse  most  readily  have  already 
been  removed. 

On  the  whole,  then,  it  may  be  said  that,  on  account  of  the  slight 
action  at  the  best,  osmosis  is  only  advantageous  under  particular 
conditions,  for  example,  in  countries  where  the  evaporated  osmosis- 
water  can  be  sold  profitably  to  the  distillery.  In  Germany,  wher- 
ever osmosis  is  still  employed,  the  simple  osmosis  apparatus  is  still 
used;  in  Austria,  on  the  other  hand,  this  apparatus  has  been  im- 
proved considerably  in  certain  respects.  These  improvements 
consist  chiefly  in  the  following  details:  The  paper  surface  is  made 
as  effective  as  possible;  the  canals  are  arranged  so  that  they  will 
not  become  stopped  up;  the  proper  relation  between  the  water  and 
the  sirup  that  enters  is  constantly  maintained ;  the  sirup  and  water 
layers  are  made  as  thin  as  possible;  the  difference  of  density 
between  the  two  liquids  is  kept  as  great  as  possible;  the  tempera- 
tures are  maintained  high,  and  the  method  of  discharge  is  a  good 


248  BEET-SUGAR  MANUFACTURE. 

one.    Of  course,  great  stress  is  laid  upon  the  quality  of  the  osmosis- 
paper. 

With  regard  to  the  method  of  using  the  osmosis  apparatus,  it 
is  so  very  simple  that  we  need  not  go  into  a  discussion  of  it  here, 
and  its  use  is  now  so  limited  in  Germany  that  it  has  become  a 
matter  of  little  interest. 

The  pure  sirups  obtained  by  osmosis  are  boiled  down  and 
brought  to  crystallization  at  a  high  temperature.  The  sugar  pro- 
duct thus  obtained  is  relatively  low  in  ash,  but  rich  in  organic  non- 
sugars,  so  that  it  is  not  so  marketable  as  the  firsts  and  brings  a  lower 
price.  The  final  molasses  produced  is  also  of  lesser  value  and  can- 
not be  utilized  for  another  desugarizing  process,  because  it  gives 
products  of  low  grade  and  is  lacking  in  those  salts  which  play  an 
important  part  in  making  the  strontia  method  effective,  for  ex- 
ample, as  well  as  those  useful  at  the  molasses  distillery. 

The  precipitation  process  is  the  best  for  the  recovery  of  sugar 
from  the  molasses  whenever  there  is  an  abundant  supply  of  cold 
water,  at  a  temperature  of  not  over  10°  to  12°  C.  (50°  to  54°  F.),  be- 
cause it  is  so  simple  that  it  does  not  cost  much  to  carry  it  out,  and 
yields  pure  juices  with  small  sugar  losses  and  adapts  itself  well  to 
the  regular  factory  work. 

The  lime  used  in  the  process  must  be  as  pure  as  possible,  con- 
taining but  little  itiagnesia.  Freshly-burned  lime  is  much  more 
effective  than  that  which  has  been  kept  for  some  time.  Particular 
stress  is  laid  upon  pulverizing  and  sifting  the  powder,  because  less 
lime  is  used  in  proportion  to  the  fineness  of  the  powder.  Foi*  th:s 
reason,  lime  that  is  soft  and  easily  pulverized  is  especially  sui  cable 
for  the  process.  Brass  sieves,  Nos.  110  to  120,  are  used  for  sifting. 

In  carrying  out  the  process,  molasses  at  14°  Brix,  and 
sometimes  much  more  dilute  than  this,  is  put  in  mixers  and  cooled 
down  to  the  temperature  of  the  cold  water.  It  is  important 
that  the  liquid  should  be  violently  stirred  or  kept  in  motion 
at  this  stage,  so  that  the  heat  will  be  quickly  given  up  to  the 
cooling  surfaces,  and  the  powdered  lime  introduced  be  mixed 
uniformly  with  the  liquid.  The  more  rapidly  this  is  accomplished 
and  the  finer  the  lime  powder  is,  the  sooner  the  lime  com- 


MOLASSES  AND  ITS  UTILIZATION.  249 

bines  with  the  sugar  to  form  the  insoluble  sucrate,  whereas,  if  the 
powder  balls  up  and  is  changed  to  hydrate,  it  becomes  inactive. 
The  greater  the  amount  of  lime  that  becomes  inactive  in  this  man- 
ner, the  greater  the  amount  of  heat  produced;  and  consequently 
the  liquid  must  remain  in  the  cooler  for  a  longer  length  of  time, 
which  gives  greater  chance  for  the  lime  to  become  slaked. 
It  is  advisable,  therefore,  to  carry  out  the  process  rapidly,  not  only 
in  the  coolers  but  later  in  the  presses,  on  account  of  the  readiness 
with  which  the  precipitated  saccharate  is  decomposed. 

In  order  to  prevent  the  balling-up  of  the  lime  into  lumps,  it 
has  also  been  proposed  to  introduce  the  lime  little  by  little  by 
sifting  the  powder,  in  the  form  of  a  fine  dust,  over  the  whole  surface 
of  the  liquid,  or  by  blowing  it  into  the  mass  with  fans.  In  this 
way  a  somewhat  smaller  amount  of  lime  is  required. 

In  the  ordinary  method  of  working,  as  a  rule,  about  80  to  120 
parts  of  lime  are  used  for  100  parts  of  sugar,  or,  in  other  words, 
from  two  to  three  times  the  theoretical  amount  necessary  for  the 
formation  of  the  trisucrate  of  lime,  and  the  quantity  increases  as 
the  water  is  warmer,  the  lime  coarser,  and  the  extent  greater  to 
which  the  removal  of  the  sugar  from  the  final  lye  is  to  be  carried. 
It  is  not  known  what  the  exact  composition  of  the  precipitated 
sucrate  is;  at  all  events  its  properties  are  different  from  the  tri- 
sucrate formed  by  boiling  lime  with  sugar-solution. 

The  sucrate  formed  in  the  cooler  must  be  immediately  filtered 
off  under  slight  pressure  in  filter-presses  with  large  compartments, 
in  order  that  the  cake  can  be  washed  readily.  The  washing  pro- 
cess is  carried  out  in  the  same  way  as  in  the  other  filter-press  work; 
but  particular  attention  must  be  paid  to  the  changing  of  the  filter- 
cloths  as  soon  as  they  begin  to  harden,  and  the  wash-water  must 
be  as  cold  as  possible.  If  the  amount  of  wash-water  is  kept  pro- 
portionally small,  the  sugar-losses  in  the  lye  will  be  diminished, 
because  all  the  wash-waters,  together  with  some  of  the  original 
mother-lye,  may  be  used  for  diluting  the  molasses. 

All  experiments  with  the  object  of  working  with  concentrated 
molasses,  so  as  to  obtain  small  amounts  of  concentrated  lyes  which 
can  be  evaporated  to  advantage  and  worked  up  for  the  potash 


250  BEET-SUGAR  MANUFACTURE. 

salts,  have  miscarried:  either  an  impure  sucrate,  hard  to  wash,  is 
obtained,  or  there  is  a  poor  sugar-yield. 

The  older  method  of  precipitating  a  part  of  the  sugar  contained 
in  the  first  lye,  by  heating  it,  is  only  used  where  it  is  considered 
advisable  to  obtain  a  charcoal  by  evaporating  and  calcining  this 
lye,  for  in  such  cases  there  must  be  precipitation  of  the  lime. 
Usually  this  first  lye,  which  amounts  to  80  to  100  per  cent,  of  the 
molasses,  is  thrown  away,  or  utilized  as  fertilizer. 

Working  the  sucrate  into  the  regular  process  is  best  accom- 
plished after  it  has  been  partially  decomposed.  If  the  sucrate, 
when  discharged  from  the  presses,  is  carried  by  means  of  a  screw- 
conveyor  to  a  vessel  provided  with  stirrer  and  there  mixed  with 
thin  juice,  it  decomposes  into  the  monosucrate  and  calcium  hydrate. 
The  mixture  acts  very  energetically  in  the  defecation  process 
directly  upon  the  diffuser-juice,  and  there  is  no  danger  of  forming, 
even  at  temperatures  above  70°  C.  (158°  F.),  the  practically  in- 
soluble trisucrate,  which  is  decomposed  with  difficulty  by  carbonic 
acid,  and  would  render  the  scums  rich  in  sugar.  This  insoluble 
trisucrate,  that  is  formed  at  high  temperatures  only,  results  when 
the  precipitated  sucrate  is  added  to  the  hot,  raw  juice  in  the  form 
of  a  thick  and  cold  paste. 

Beet-sugar  factories  which  only  work  up  their  own  molasses 
are  accustomed  to  add  with  the  sucrate  from  2  to  2£  per  cent,  of 
lime  to  the  beet-juices,  or  exactly  as  much  as  is  usually  used  for 
defecation.  When  it  is,  however,  considered  advantageous  to 
buy  molasses  and  remove  the  sugar,  this  amount  of  sucrate  would 
give  too  much  lime  for  defecation,  and  the  carbonatation  would 
be  unnecessarily  burdened.  In  such  cases  it  is  advisable  to  mix 
the  excess  of  trisucrate  with  considerable  thin  juice,  and  to  then 
filter  off  the  precipitated  calcium  hydrate,  which  can  be  done  with- 
out difficulty,  in  filter-presses.  After  sweetening  off,  this  calcium 
hydrate  may  be  added  to  the  dilute  molasses  in  which  it  dissolves 
with  the  formation  of  the  monosucrate,  and  hence  caustic  lime 
will  be  saved. 

Although  this  precipitation  process  is  a  desirable  one  for  the 
recovery  of  sugar  from  molasses  apart  from  working-up  of  beets, 


MOLASSES  AND  ITS  UTILIZATION.  251 

on  account  of  the  ready  decomposition  of  the  sucrate,  yet  the  chief 
advantages  are  obtained  only  when  it  is  carried  out  in  connection 
with  the  beet-work,  because  these  sucrates  furnish  without  addi- 
tional expense  the  requisite  amount  of  lime  for  a  good  defecation, 
while  the  other  expenses  of  operation,  where  this  mutual  advantage 
is  gained,  are  very  slight. 

While  the  sugar-liquors  recovered  from  the  sucrate  usually 
have  a  purity  of  90°  to  94°,  which  is  at  least  as  high  as  that  of 
the  beet-juic^,  it  is  nevertheless  true  that  the=e  juices  are  less 
readily  crystallizable  than  those  obtained  directly  from  the  pure 
beets.  For  this  reason  it  is  a  fact  that  the  yield  of  firsts  from 
massecuites  is,  with  equal  purity,  always  greater  in  those  cases 
where  the  pure  beet-juice  is  worked  up  than  when  it  has  been 
mixed  with  sucrate.  It  appears  as  if  this  lack  of  tendency  to 
crystallize  is  caused  by  the  presence  of  certain  injurious  non- 
sugars,  and  in  particular  certain  lime-salts,  which  are  not  removed 
by  defecation,  but  remain  in  the  sucrates  and  are  constantly  carried 
back  to  the  beet-juice.  Consequently  the  amount  of  these  sub- 
stances steadily  increases  (especially  the  raffinose,  which  is  pre- 
cipitated by  the  lime),  so  that  its  action  upon  the  crystallization 
tends  to  increase  from  year  to  year.  It  is,  therefore,  absolutely 
necessary  that  once  in  a  while  the  residual  molasses  shall  be 
thrown  out  altogether,  say,  perhaps,  every  two  or  three  years, 
depending  on  the  quality  of  the  beets. 

If  these  precautions  are  taken,  the  diminution  in  the  yield  of 
firsts,  as  well  as  the  injury  to  the  quality  of  the  sugar,  is  kept 
within  certain  limits;  although  it  is  unquestionable  that  this 
change  in  the  nature  of  the  product  is  disadvantageous  for  refining. 
This  method  of  purifying  the  molasses  is  successful  only  as  long 
as  the  raw  sugar  obtained  is  not  valued  at  a  price  lower  than  that 
brought  by  pure  raw  sugar. 

Electrolytic  processes  have  been  recommended  for  extracting 
sugar  from  molasses  as  well  as  from  juice,  employing  dialysis 
through  a  membrane.  These  processes  have  considerable  in- 
terest, as  they  attempt  to  recover  not  only  large  amounts  of 
sugar  but  non-sugars  as  well,  and  it  is  in  the  latter  that  the  profit 


252  BEET-SUGAR  MANUFACTURE. 

is  looked  for.  A  membrane  impermeable  to  sugar  and  a  peculiar 
mercury  cathode  are  used.  The  alkali  metals  set  free  by  the 
electric  current  at  the  cathode  dissolve  in  the  mercury  which  is 
being  continually  removed  from  the  cathode  space.  In  the  upper 
half  of  the  apparatus,  the  amalgams  of  the  alkali  metals  are 
decomposed  by  water,  the  mercury  constantly  flowing  back  to 
the  cathode.  Acids  pass  through  the  membrane  to  an  iron 
anode  where  they  form  iron  salts  which  all  the  time  are  being 
converted  to  lime  salts  by  added  lime,  and  separate  out  as  the 
solution  concentrates. 

The  purity  of  the  molasses  only  rises  to  75,  so  that  only  a  small 
amount  of  sugar  of  little  value  is  recovered.  Whether  there  is 
sufficient  profit  in  the  by-products  to  make  the  process  pay  is 
very  doubtful. 

The  Use  of  Molasses  as  Fodder. — The  food-value  of  molasses 
depends  for  the  most  part  upon  the  sugar-content,  and  also  to  some 
extent  upon  action  of  salts  upon  digestion.  It  is,  therefore, 
not  only  an  easily-digested  food,  but  also  a  condiment,  exciting 
the  appetite  of  the  animal,  and  causing  it  to  eat  and  digest  forms 
of  fodder  it  would  not  care  for  without  the  molasses. 

Since  the  great  viscosity  of  molasses  in  the  cold  condition 
diminishes  its  value  as  a  fodder,  particularly  when  used  on  small 
farms  on  which  necessary  arrangements  for  warming  and  diluting 
are  wanting,  it  is  usually  preferable  to  mix  it  with  turf-meal,  or  other 
fodder  which  will  absorb  the  molasses.  Such  a  mixture  forms  a 
dry  and  more  or  less  brittle  mass  which  can  easily  be  broken  up 
into  small  pieces. 

The  mixture  is  usually  prepared  at  the  sugar-factory  by  means 
of  suitable  machines  for  mixing  the  absorbent  material  with  the 
hot  molasses.  The  temperature  of  the  molasses  should  not,  as 
a  rule,  exceed  80°  C.  (176°  F.),  because  otherwise  the  fodder  cools 
down  too  slowly,  and  frequently  there  is  an  after-heating  if  the 
mixture  is  stored  in  heaps.  When  the  molasses  is  mixed  with 
malt-germs,  or  any  similar  substance  which  turns  brown  on  heat- 
ing or  has  an  acid  reaction,  the  temperature  should  be  kept  below 
80°  C. 


MOLASSES  AND  ITS  UTILIZATION.  253 

When  the  fodder  has  thus  been  mixed,  it  must  be  completely 
cooled  in  flat  heaps  before  it  can  be  placed  in  bags  or  in  larger 
heaps.  It  is  best  to  use  the  fodder  as  soon  as  possible  after  its 
preparation,  for  it  has  a  tendency  to  spoil  on  keeping.  A  moist 
molasses-fodder  spoils  readily,  and  is  then  injurious  to  the  animal. 
The  molasses  should  not  be  heated  by  introduction  of  live  steam, 
but  by  closed  coils,  if  it  has  already  been  diluted  to  80°  Brix.  A 
fodder  prepared  by  using  a  molasses  of,  say,  78°  Brix,  does  not 
keep  so  well  and  separates  readily  from  the  mixture,  particularly 
in  summer. 


CHAPTER  XXIII. 
THE    BOILER-HOUSE. 

THIS  is  not  the  place  for  going  into  a  detailed  discussion  of  the 
economy  and  technique  of  the  boiler-house  and  the  firing,  but  only 
those  points  will  be  brought  out  which  are  peculiar  to  the  conduct 
of  the  boiler-house  of  a  sugar-factory.  First  of  all,  it  must  be 
emphasized,  however,  that,  if  there  is  to  be  economy  observed  in 
the  use  of  fuel,  there  must  be  a  good  system  of  boilers,  properly- 
arranged  grates  with  good  firing,  and  the  boiler-house  must  be  in 
constant  touch  with  the  factory  work.  As  it  is  always  difficult 
to  obtain  good  firemen  for  the  short  working  period  of  a  beet-sugar 
factory,  mechanical  stokers  have  been  introduced  to  a  considerable 
extent,  which  permit  the  utilization  of  less  expensive  forms  of  fuel. 
Connected  with  these  artificial  stoking  arrangements  there  should 
be  an  apparatus  for  mechanical  transportation  of  the  fuel.  The  work 
necessary  in  superintending  the  operation  of  this  machinery  must 
be  carefully  done,  such  as,  for  example,  weighing  the  fuel,  measur- 
ing the  feed-water,  examining  the  flue-gases  by  taking  special 
samples,  or  sampling  by  a  mechanical  device;  controlling  the  steam- 
pressure  by  recording  manometers,  measuring  the  temperature 
of  the  boiler  feed-water  and  of  the  flue-gases  by  self-recording 
thermometers,  and  controlling  the  draft  by  measuring  it  at  the 
boilers  and  in  the  chimney. 

Since  beet-sugar  factories  require  their  fuel  just  at  a  time  when 
other  users  are  in  great  need  of  coal  and  the  business  of  the  rail- 
roads is  very  much  rushed,  it  is  necessary  to  arrange  a  large 
part  of  the  coal  supply  for  summer  delivery.  In  the  case  of 
lignite  coals  such  early  delivery  should  be  avoided  as  far  as  pos- 

254 


THE  BOILER-HOUSE.  255 

sible.  They  keep  well  only  when  piled  in  a  compact  mass  which 
is  not  feasible  if  the  delivery  is  not  practically  all  at  once.  Even 
many  other  kinds  of  coal  lose  in  value  when  not  stored  carefully 
in  appropriate  manner.  They  become  heated  by  oxidation  of 
iron  pyrite  and  hydrocarbon  constituents  and  often  become 
ignited.  To  prevent  heating,  it  has  been  recommended  to  drench 
the  coal  with  plenty  of  water,  if  its  temperature  rises  above  50° 
(1±2°  F.).  Air  cooling  is  not  recommended,  as  the  air  circulation 
will  be  greatest  where  the  coal  is  hottest.*  The  surest  means  of 
quenching  already  ignited  coal  is  by  means  of  carbon  dioxide. 
Coal  storage  under  cover  is  v  >ry  desirable  but  expensive.  In  all 
cases  of  prolonged  storing  of  coal  it  is  necessary  to  keep  constant 
watch  of  its  temperature  as  observed  from  thermometers  inserted 
in  the  heaps,  so  that  timely  precautions  can  be  taken  should  a 
steady  rise  in  temperature  be  shown. 

The  particular  conditions  prevailing  in  the  boiler-houses 
of  a  sugar-factory  are  partly  favorable  and  partly  unfavorable. 
It  is  very  advantageous  to  have  a  supply  of  pure  and  hot  feed- 
water,  which  is  furnished  by  the  distilled  water  from  the  evap- 
orat ing-pans.  The  temperature  of  this  water  is  determined  by  the 
pressure  under  which  the  steam  is  condensed.  The  hottest  water 
comes  from  the  heating-chambers  of  the  juice-heaters  and  the  first 
member  of  the  multiple  effect,  and  has  a  temperature  of  from  110° 
to  120°  (230°  to  248°  F.).  In  some  factories  this  hot  water  is 
collected  under  pressure  in  closed  retainers,  and  is  pumped  sepa- 
rately from  the  other  water  into  the  boilers,  so  that  it  still  has  a 
temperature  of  something  over  100°  (212°  F.)  when  it  enters 
the  boilers.  Since,  however,  this  very  hot  water  is  insufficient  in 
quantity,  and  it  is  necessary  to  utilize  the  condensed  steam  from 
the  other  apparatus,  which  have  a  temperature  of  less  than 


*  This  is  not  in  accord  with  American  practice.  Coal  here  is  kept  as 
dry  as  possible,  moist  coal  being  considered  a  greater  fire  risk.  The 
practice  of  the  large  coal  companies  here  is  to  dig  out  the  hot  coal  and 
expose  it  to  the  air  by  moving  the  heap.  Small  steel  flasks  of  liquid 
carbonic  acid  which  are  closed  with  fusible  plugs  are  sometimes  placed 
in  the  heaps. — TRANSLATORS. 


256  BEET-SUGAR  MANUFACTURE. 

100°  (212°  F.),  it  is  evident  that  all  of  the  feed-water  may  be 
collected  together  in  the  same  vessel  to  advantage.  In  this  way 
the  hottest  water  becomes  mixed  with  the  coldest,  and  the 
temperature  of  the  mixture  is  in  the  neighborhood  of  100°  C. 
If  the  condensed  vapor  from  the  sirup  effects,  which  have  temper- 
atures around  75°-SO°  (167°-176°  F.),  is  only  used  in  exceptional 
cases  for  feeding  the  boilers,  but  is  ordinarily  utilized  for  other 
purposes  in  the  factory,  then  the  temperature  of  the  feed-water 
should  not  sink  below  90°-95°  (194°-203°  F.).  The  pumps 
required  for  feeding  the  boilers  work  without  any  trouble  with 
the  hot  water  if  they  are  provided  with  check-valves  on  the 
suction-pipe,  and  if  the  water  runs  to  the  pumps. 

This  hot  water  of  condensation  may  frequently  contain  sub- 
stances which  will  act  injuriously  upon  the  boilers,  such  as,  for 
example,  sugar  and  oil.  The  ammonia  contained  in  the  condensed 
water,  on  the  other  hand,  exerts  no  injurious  effect,  but  is  helpful, 
if  anything,  as  an  alkali. 

Injuries  to  the  boilers  caused  by  sugar  may  be  of  two  kinds, 
namely,  either  of  a  chemical  or  of  a  mechanical  nature.  Which 
influence  makes  itself  most  felt  depends  upon  the  amount  of 
sugar  reaching  the  boilers.  If  only  extremely  small  quantities  of 
sugar  are  fed  into  the  boilers  little  by  little,  then  the  sugar  becomes 
decomposed  more  or  less  quickly,  according  to  the  temperature  of 
the  water  in  the  boiler,  and  acids  of  different  compositions  are 
formed  without  precipitation  of  perceptible  amounts  of  solid 
decomposition  products.  If  large  amounts  of  sugar  enter  a  boiler 
at  any  time,  the  sugar  becomes  burned  at  the  hottest  portions  of 
the  tubes;  and  in  this  way  a  layer  of  porous  charcoal  is  formed 
whose  thickness  increases  so  rapidly  that  the  metal  under  it 
becomes  overheated,  and,  on  account  of  the  pressure  exerted 
from  within,  bulges  out.  Such  action  may  be  produced  by  a 
layer  of  but  a  few  millimeters  in  thickness. 

This  sort  of  injury  to  the  boiler  by  the  introduction  of  water 
containing  sugar  is  by  all  means  the  most  serious  that  can  take 
place,  beca-use  it  is  effected  very  rapidly,  and  within  a  few  hours 
after  any  large  amount  of  sugar  has  passed  into  the  boiler.  There 


THE   BOILER-HOUSE.  257 

is  no  remedy  for  this,  other  than  to  shut  down  the  whole  boiler- 
house  immediately,  or  to  cut  out  that  boiler  containing  the  sugar 
and  blow  off  the  boiler-water.  There  should  be  no  hesitation  in 
such  cases  to  resort  to  extreme  measures;  for  the  troubles  in  the 
other  parts  of  the  factory,  which  may  result  from  shutting-off  of 
the  steam,  are  by  no  means  so  serious  as  the  harm  which  may  bs 
done  by  bulging  the  boiler  sheets  during  the  campaign.  The 
higher  the  steam-pressure  within  the  boilers,  the  more  rapid 
is  the  decomposition  of  any  sugar  present;  consequently,  in  the 
the  case  of  boilers  with  high  steam-pressure,  particular  attention 
to  this  detail  is  required.  If  the  bulges  are  not  too  deep,  and  the 
boiler-plate  is  of  good  material,  it  is  often  possible  to  force  back 
the  swelling,  and  in  a  short  time  make  the  boiler  in  good  condition 
again.  In  all  cases  this  inexpensive  method  of  getting  over  the 
difficulty  should  always  be  tried  before  going  to  the  tedious  and 
troublesome  work  of  changing  tubes  or  plates. 

If  the  given  precautions  are  taken  with  respect  to  juice- 
leaks  in  the  evaporating-plant,  and  if  the  condensed  water  of 
the  preheaters,  in  which  the  vapor-pressure  is  greater  in  the 
juice-space  than  in  the  steam-chambers,  and  that  from  the 
vacuum-pans,  be  not  taken  for  the  boiler-feed,  one  can  feel 
fairly  certain  that,  in  the  ordinary  conduct  of  the  work,  no 
large  amount  of  sugar  will  get  into  the  boilers.  The  state  of 
affairs  is  quite  different  when  there  are  troubles  in  evapora- 
tion or  vacuum-pan  plant,  and  the  vacuum  off  the  apparatus 
so  that  the  pressure  in  the  juice-chamber  is  equal  to  that  in 
the  heating-space.  Then,  if  there  is  a  leaky  pipe  or  a  steam-coil, 
it  is  easily  possible  for  large  amounts  of  sugar  to  get  into  the  steam- 
space  and  thence  into  the  boiler  feed-water.  Consequently,  when 
there  is  any  such  trouble  hi  the  factory,  the  feed- water  should  be 
immediately  examined  to  see  if  it  contains  sugar,  first  of  all  by 
tasting  it,  then  by  a  laboratory  test.  In  case  an  appreciable  quan- 
tity of  sugar  is  found,  it  is  unsuitable  for  the  boilers,  and  fresh 
water  must  be  used  in  its  place. 

The  second  kind  of  injury  that  may  be  produced  by  the  sugar 
is  of  a  chemical  nature,  and  the  nature  of  this  is  a  corrosion  brought 


258  BEET-SUGAR  MANUFACTURE. 

about  by  the  action  of  the  acids  produced  in  the  decomposition 
of  the  sugar  upon  the  boiler-plate.  The  nature  and  extent  of  the 
corrosion  depends,  in  the  first  place,  upon  the  amount  of  sugar 
in  the  boiler,  then  upon  the  steam-pressure,  or,  what  is  the  same 
thing,  the  temperature,  and,  finally,  upon  the  duration  of  the 
action.  The  higher  the  temperature  of  the  water  in  the  boiler, 
the  more  rapid  will  be  the  conversion  of  sugar  into  these  acids. 
Whereas,  in  boilers  used  merely  for  boiling  purposes  in  which  the 
temperature  as  a  rule  does  not  exceed  two  atmospheres  (30  Ibs.), 
the  sugar  is  only  slowly  decomposed,  in  those  boilers  with  high- 
pressure  steam  of,  say,  six  atmospheres  (90  Ibs.  =  164°  C.  or  327° 
F.),  it  takes  place  very  rapidly,  as  the  acids  formed  by  the  decom- 
position act  energetically  upon  the  iron  at  these  high  tempera- 
tures and  corrosion  is  rapid  and  considerable. 

It  is  absolutely  impossible  to  prevent  the  introduction  of  small 
quantities  of  sugar  into  the  boilers  during  the  progress  of  the  work. 
In  order  to  prevent  these  injuries,  the  boiler  feed-water  must  be 
made  alkaline  by  addition  of  soda,  and  this  alkalinity  must  be  regu- 
larly tested  at  every  water-cock  and  in  each  boiler.  This  alkalinity 
should  not  be  made  too  high,  as  in  that  case  the  boiler-water  foams 
too  much;  as  a  rule,  an  alkalinity  is  desirable  such  that  100  c.c. 
of  the  boiler-water,  when  titrated  with  rosolic  acid  as  indicator, 
will  require  10  c.c.  of  tenth-normal  acid  to  neutralize  it.  If  sud- 
denly the  alkalinity  is  found  to  be  greatly  diminished,  it  is  a  sign 
that  sugar  has  gone  into  the  boiler,  and  in  fact  the  amount  of 
sugar  can  be  calculated  by  the  diminution  in  alkalinity;  0.0114 
gram  of  sugar  will  produce  enough  acid  to  neutralize  1  c.c.  of 
tenth-normal  alkali,  or  two  kilograms  of  sugar  are  equivalent  to 
approximately  one  kilogram  of  sodium  carbonate  (soda). 

It  is  absolutely  necessary  to  examine  the  water  in  every  water- 
cock  of  each  boiler,  for  it  is  easily  possible  that  one  boiler  may 
contain  more  sugar  than  another  boiler,  because  of  the  fact  that 
it  has  just  been  fed  with  water  containing  sugar.  Furthermore, 
an  immediate  examination  of  the  water  in  all  of  the  boilers  is 
necessary  when  the  well-known  odor  of  decomposed  sugar  is  per- 
ceptible in  the  steam,  or  if  there  is  a  noticeable  increase  of  color 


THE  BOILER-HOUSE.  259 

in  the  boilrr-wutor  and  it  begins  to  foam  strongly.  A  dark  colora- 
tion of  the  boiler-water  is  of  itself  not  harmful  as  long  as  the  water 
reacts  alkaline. 

A  certain  amount  of  protection  against  the  action  of  the  sugar 
is  afforded  by  a  mineral  layer  upon  the  boiler-plates.  There  is 
always  slight  scale,  on  account  of  the  fact  that,  at  the  beginning 
of  the  campaign  as  well  as  on  Sundays,  the  boilers  must  be  fed 
with  spring-water,  and  the  salts  contained  in  it  are  gradually 
deposited  upon  the  boiler-plates.  This  scale  is,  however,  not  to 
be  relied  upon,  as  frequently  the  deposits  become  loosened  and 
drop  off. 

Rules  for  preventing  injury  to  boilers  by  sugar  may  be 
summarized  as  follows: 

1.  Use  condensed  water  from  the  evaporators  only  for  feed- 
ing boilers;  and  examine  for  sugar  before  it  is  used,  not  only 
at  the  beginning,  but  always  when  the  vacuum  in  the  evaporators 
is  abnormal  through  any  trouble  in  the  factory. 

'2.  Maintain  a  definite  alkalinity  of  the  boiler-water  by  adding 
soda  to  the  feed,  and  regularly  examine  the  water  in  each  boiler 
for  alkalinity. 

3.  Cut  out  at  once  any  boiler  in  which,  in  spite  of  the  pre- 
caution above  mentioned  (2) ,  tne  boiler-water  suddenly  shows  an 
acid  reaction,  or  if  it  becomes  dark-colored  and  foams  badly. 

4.  Immediately  examine  the  boiler-water  as  soon  as  the  well- 
known  odor  of  decomposed  sugar  is  perceptible,  or  when  the  in- 
dicator glasses  in  the  side  of  the  boiler  show  that  the  water  is 
becoming  dark-colored. 

5.  The  boilers  should  be  fed  at  the  beginning  of  the  campaign 
with  spring-water,  so  that  a  protecting  layer  of  mineral  deposit 
will  be  formed  upon  the  boiler-plates. 

6.  Condensed  water  should  not  be  used  for  feeding  the  boilers 
at  the  beginning  of  the  campaign,  until  it  has  become  perfectly 
clear  and  colorless. 

The  water  obtained  from  the  condensation  of  the  engine-exhaust 
contains  some  of  the  oil  which  was  used  for  lubricating  the  steam- 
cylinders.  Since  vegetable  or  animal  oils  or  fats  would  be  saponified 


260  BEET-SUGAR   MANUFACTURE. 

by  the  hot  water  in  the  boilers  into  free  fatty  acids,  and  the  latter 
would  attack  the  iron,  it  follows  that  oils  of  this  character  should 
not  be  used.  This  causes  no  trouble,  because  it  is  possible  to 
obtain  suitable  mineral  oils  which  are  composed  of  pure  hydro- 
carbons and  cannot  form  acids.  Even  oils  of  the  latter  type, 
however,  can  cause  harm  if  they  enter  the  boilers  in  large  amounts, 
because  they  store  up  heat  and  thus  make  steaming  more  difficult, 
and  tend  to  form  tough  lumps  with  the  loose  scums  that  are  present 
in  almost  every  boiler-water.  These  lumps  tend  to  deposit  on  the 
heating-tubes  and  prevent  the  heat-transference  to  the  water, 
so  that  the  plates  may  be  overheated. 

Such  troubles  can  be  prevented  best  by  an  apparatus  for 
removing  oil  placed  in  the  exhaust-steam  pipes  before  they  reach 
the  evaporating-pans,  which  serves  to  remove  the  greater  part 
of  the  oil;  in  this  way  any  injurious  action  of  the  oil  in  causing 
overheating  of  the  boiler-plates  is  prevented.  Filters  arranged 
so  as  to  filter  off  the  oil  from  the  water  have  not  proved  practical. 
A  part  of  the  oil  may  also  be  removed  by  collecting  the  boiler 
feed-water  in  tanks  provided  with  an  overflow.  The  finely-divided 
oil  in  the  water  then  has  time  to  collect  to  a  considerable  extent 
upon  the  surface  of  the  water  and  there  overflow.  It  is  self- 
evident  that  it  is  desirable  not  to  use  too  great  an  amount  of  oil 
in  lubricating  the  cylinders,  as  an  excess  tends  to  increase  the 
amount  that  is  carried  over  into  the  condensed  water. 

The  oily  scum  has  an  unpleasant  action  in  still  another  respect. 
Before  it  settles  to  the  bottom  it  floats  in  the  form  of  a  loose  mass, 
and  often  stops  up  the  water  gauges.  This  difficulty  may  be 
overcome  by  placing  a  bent  piece  of  sheet-metal  inside  on  the 
front  head  of  the  boiler,  extending  perpendicularly  in  front  of 
the  water-gauge  supports,  dipping  into  the  water  down  to  the 
heating-tubes  and  nearly  reaching  up  to  the  top  of  the  boiler. 
In  this  way  a  place  is  formed  where  the  water  is  relatively  quiet, 
so  that  any  scum  which  might  enter  from  underneath  must  again 
sink  to  the  bottom,  while  at  the  top  there  is  no  danger  of  any 
scum  getting  in,  even  when  the  contents  of  the  boiler  foam  badly. 

The  escaping  gases  of  combustion  have  usually  a  temperature 


THE  BOILER-HOUSE.  261 

of  200°-300°  (390°-570°  F.),  but  often  owing  to  the  forcing  of  the 
boiler  as  high  as  400°  (750°  F.).  The  temperature  is  always  lower 
at  the  beginning  of  the  campaign  than  at  the  close,  as  it  is  in- 
creased by  the  poorer  heat  transference  due  to  scale  in  the  boilers 
and  rust  on  the  tubes.  This  large  amount  of  heat  can  be  utilized 
by  placing  a  feed-water  heater  in  the  main  flue,  which  reduces  it  to 
140°-150°  (284°-302°  F.),  or  by  a  tubular  superheater.  Feed- 
w ater  heaters  have  often  proved  their  utility,  but  placing  them  in 
the  main  flue  has  now  been  given  up,  since  at  that  point  the  heat 
is  too  low,  too  much  heating  surface  being  necessary.  Super- 
heaters are  now  nearly  always  built  where  the  temperature  of  the 
gases  is  about  500°  (930°  F.),  or  directly  behind  the  boiler-tubes. 
In.  some  boiler-houses  boilers  using  high-pressure  steam  are 
placed  beside  others  of  lower  pressure,  the  former  furnishing 
steam  for  the  engines  with  a  pressure  of  six  to  eight  atmospheres 
(90-120  Ibs.  steam-pressure),  and  the  latter  steam  for  evaporating 
purposes  with  a  pressure  of  only  two  or  three  atmospheres 
(30-45  Ibs.).  This  boiler  division  originated  because  newer 
boilers  are  constructed  for  higher  pressures  than  the  older  ones 
and  when  it  is  desirable  to  still  utilize  the  latter  there  is  no  ob- 
jection to  the  arrangement.  If,  on  the  other  hand,  it  is  believed 
that  the  work  is  more  advantageously  conducted  when  this  is 
done  the  idea  is  erroneous.  With  a  definite  amount  of  coal  nearly 
as  much. steam  at  six  atmospheres'  pressure  is  produced  under 
the  same  conditions  as  at  three  atmospheres,  for  although  the 
difference  in  temperature  between  the  heating-gases  and  the  con- 
tents of  the  boiler  is  about  twenty  degrees  less  in  the  former 
case,  yet  the  amount  of  heat  taken  up  is  not  much  greater,  because 
the  transmission-coefficient  increases  at  the  higher  temperature. 
The  amount  of  heat  lost  by  being  carried  away  by  the  flue-gases  is, 
therefore,  about  the  same  in  both  cases.  Furthermore,  steam  at 
six  atmospheres  can  be  changed  into  a  pressure  of  three  atmos- 
pheres by  means  of  a  reducing-valve  without  the  loss  of  any  heat. 
It  is  evident,  therefore,  that  there  is  no  particular  advantage  to  be 
gained  by  dividing  boilers  into  two  systems,  and  it  certainly 
has  disadvantages,  particularly  because  it  requires  more  attention. 


262  BEET-SUGAR    MANUFACTURE. 

A  battery  of  boilers  of  which  all  are  at  the  same  pressure  can  be 
fired  to  much  better  advantage  than  when  there  are  two  series  of 
boilers,  one  at  a  higher  steam-pressure  than  the  other.  The  de- 
mands of  one  are  quite  different  from  those  of  the  other,  and  it  is 
much  harder  to  run  boilers  of  a  divided  battery  economically  and 
fire  them  properly.  If  the  irregularities  in  the  use  of  steam  in  the 
factory  are  distributed  throughout  the  whole  boiler  system,  or,  in 
other  words,  upon  practically  three  times  as  many  boilers  than 
when  two  systems  are  used,  then  the  firing  need  be  only  slightly 
increased  or  diminished  to  meet  the  new  conditions,  and  it  is  done 
uniformly.  In  a  separated  system  of  boilers  a  double  system  of 
steam-piping  is  necessary,  and  the  cooling-losses  are  greater  than 
when  one  pipe  of  large  dimensions  is  used. 

Particular  attention  must  be  paid  to  the  boilers  after  the  cam- 
paign is  over.  As  the  boilers  are  used  only  two  or  three  months 
in  the  year,  and  the  remaining  time  are  cold,  they  are  likely  to 
suffer  in  common  with  all  other  iron  parts  in  the  factory  by  cor- 
roding badly,  unless  particular  precautions  are  taken.  The  best 
means  of  preventing  the  formation  of  rust,  both  on  the  inside  and 
outside  of  the  boilers,  and  particularly  in  the  flues,  is  to  thor- 
oughly clean  and  dry  them.  The  flues  must  be  thoroughly 
freed  from  flue-ashes  and  soot,  the  scale  on  the  inside  of  the  boiler 
removed,  and  finally  all  the  boiler  and  masonry  must  be  thoroughly 
dried  by  small  fire.  It  is  not  advisable  to  cover  the  boiler  with  any 
rust  preventative;  sometimes  it  is  recommended  to  cover  the  inside 
with  tar,  but  it  is  very  doubtful  whether  this  does  much  good,  and 
there  is  danger  to  workmen,  as  the  hot  tar  readily  evolves  com- 
bustible gases.  Similar  care  should  be  given  to  the  superheaters 
and  feed-water  heaters,  after  the  campaign,  as  to  the  boilers. 


CHAPTER  XXIV. 
THE   LIME-KILNS. 

OP  the  different  types  of  lime-kilns  two  have  proved  most 
suitable  for  the  sugar  factory:  the  so-called  Belgian  kiln,  which  is 
heated  solely  by  means  of  the  coke  which  is  thrown  into  the  kiln 
from  the  top  together  with  the  limestone,  and  the  kiln  with  re- 
generator firing,  in  which  the  heating  is  wholly  or  in  part  produced 
by  means  of  an  exterior  hearth.  In  general  it  may  be  said  that 
less  fuel  is  required  by  the  Belgian  kiln;  since,  however,  it  is 
necessary  to  use  good  coke  with  as  low  ash  as  possible,  while  the 
other  type  permits  the  use  of  a  cheaper  grade  of  fuel,  there  is  prac- 
tically no  difference  in  the  expense  of  operating. 

A  good  lime-kiln,  or  -burner,  when  worked  properly,  should  yield 
well-burned  lime  and  a  saturation-gas  rich  in  carbonic-acid  gas 
(carbon  dioxide). 

Choice  of  limestone  is  by  no  means  a  matter  of  minor  import- 
ance to  the  industry,  although  its  suitability  cannot  be  determined 
in  many  cases  by  chemical  analysis  alone,  because  usually  the  ana- 
lytical results  do  not  show  whether  it  will  be  difficult  or  easy  to  con- 
vert the  limestone  into  lime,  or  whether  the  impurities  will  exert 
a  harmful  influence.  This  is  determined  more  readily  by  the  outer 
appearance  and  structure  of  the  limestone,  and  the  injurious  effect 
of  impurities  does  not  so  much  depend  upon  the  amount  present 
as  upon  the  way  they  are  distributed  throughout  the  mineral.  At 
the  same  time  it  is  safe  to  assume  that  a  limestone  in  which  the 
chemical  analysis  shows  the  presence  of  considerable  quantities  of 
foreign  constituents  is  lass  suitable,  and  whenever  possible  it  should 
be  replaced  by  a  purer  variety.  These  impurities  are  capable 

263 


264  BEET-SUGAR   MANUFACTURE. 

not  only  of  contaminating  the  juices  in  defecation,  but  they 
may  cause  trouble  in  the  lime-kilns.  The  presence  of  silicic  acid 
has  the  effect  of  strongly  lessening  the  slaking  power  of  the  lime; 
in  some  cases  as  little  as  six  per  cent,  of  silica  will  cause  the  lime 
.to  become  "dead  burned"  in  a  short  time,  so  that  it  will  not  slake 
quickly  with  evolution  of  heat.  Alumina,  iron,  and  manganese  of 
themselves  do  not  exert  any  harmful  influence,  but  when  iron 
is  present,  together  with  alumina  and  silicic  acid,  it  favors  the  de- 
composition of  any  clay,  and  there  is  a  tendency  towards  "dead 
burning."  The  presence  of  sulphur  either  in  the  limestone  or  in 
the  fuel  is  always  harmful,  because  it  causes  formation  of  gypsum 
"'(calcium  sulphate),  and  the  latter  acts  injuriously  upon  the  lime. 
Alkalies,  which  are  usually  present  only  to  an  inappreciable  amount, 
can  cause  harm  if  they  exist  to  any  extent  in  certain  parts  of  the 
limestone,  for  they  aid  the  decomposition  of  other  constituents'  by 
acting  as  a  flux.  Naturally,  the  action  of  all  these  impurities  depends 
upon  the  duration  of  the  lime-burning  and  the  temperature  as 
well  as  upon  the  structure  of  the  limestone. 

Burning  of  limestone  accomplishes  dissociation  of  calcium  car- 
bonate into  calcium  oxide  and  carbon  dioxide  (or  carbonic-acid 
gas);  and,  like  all  such  dissociation  phenomena,  it  depends  upon 
the  temperature  and  pressure  of  the  gas.  At  a  temperature  of 
about  800°  C.  (or  1475°  F.)  there  is  already  slight  dissociation, 
but  it  becomes  appreciable  only  when  900°  C.  (1650°  F.)  is 
reached.  At  temperatures  below  this  decomposition  point,  which 
is  a  dull-red  heat,  the  burned  lime  has  a  strong  tendency  to 
absorb  carbon  dioxide,  although,  as  is  well  known,  it  does  not  do 
this  at  ordinary  temperatures  when  exposed  to  dry  carbon  dioxide. 
For  this  reason  it  follows  that  the  carbon  dioxide  set  free  must 
be  removed  as  fast  as  possible  from  the  kiln.  The  tendency  for 
any  chemical  reaction  to  take  place  completely  is  always  greater 
when  one  of  the  products  of  the  decomposition  is  removed. 

For  practical  working  of  lime-kilns  it  is  always  sufficient  to 
heat  the  limestone  for  a  few  hours  at  a  temperature  somewhat 
over  1000°  C.  (1850°  F.).  The  highest  temperatures  that  should 
be  attained  in  the  burning  are  between  1200°  and  1300°  C.  (2200° 


THE  LIME-KILNS.  265 

to  2375°  F.)/^This  is  sufficiently  high  to  completely  convert  large 
pieces  of  limestone  into  lime.  Higher  temperatures  should  be 
avoided,  particularly  for  any  long  period  of  time.  Even  perfectly 
pure  calcium  carbonate,  when  decomposed  by  five  or  six  hours' 
heating  at  temperatures  of  about  1600°  C.  (2900°  F.),  becomes 
converted  into  a  condition  such  that  it  does  not  slake  with  water 
until  it  has  stood  in  contact  with  it  for  about  one  day,  being  prac- 
tically dead  burned.  If  it  contains  small  amounts  of  silicic  acid 
the  same  effect  occurs  at  lower  temperatures  and  in  shorter  time. 

The  size  of  the  burner,  or  kiln,  depends  upon  the  amount  of 
lime  which  it  is  desired  to  produce  in  24  hours.  When  it  is  cheaper 
to  buy  the  lime  than  to  make  it,  only  an  amount  sufficient  to 
yield  the  necessary  quantity  of  carbon-dioxide  gas  should  be 
burned.  Since  for  burning  100  parts  of  limestone  about  10  or 
12  "parts  of  fuel  are  required  (coke  or  coal),  and  there  is  about 
the  same  weight  of  carbon  in  12  parts  of  coke  as  in  100  of  lime- 
stone, it  follows  that  about  half  of  the  carbon  dioxide  comes  from 
the  coal  and  the  remainder  from  the  limestone.  If,  then,  the  gas 
from  the  kiln  contains  twice  as  much  carbonic  acid  as  was  originally 
present  in  the  limestone,  and  say  two-thirds  of  the  gas  that  is 
passed  into  the  juices  during  carbonatation  is  actually  utilized, 
it  follows  that  the  carbonic  acid  produced  by  the  kiln  will 
saturate,  or  carbonatate,  about  one-third  as  much  more  lime 
as  is  produced  by  the  kiln.  This  additional  amount  of  lime  can 
be  purchased. 

The  size  of  a  lime-kiln  is  also  regulated  by  the  capacity  of  the 
gas-pump.  The  more  rapidly  the  gas  is  removed  from  the  kiln 
the  quicker  is  the  conversion  of  limestone  into  lime  and  the 
higher  the  layer  which  reaches  the  maximum  temperature  of  about 
1200°  C.,  and,  in  fact,  this  maximum  temperature  is  higher  for 
the  same  reason.  The  greater  the  activity  of  the  kiln  the  greater 
the  yield  of  both  lime  and  carbonic  acid,  while  the  consumption 
of  fuel  is  relatively  less.  The  zone  of  maximum  temperature  is 
larger  when  the  burner  is  taller  with  correspondingly  smaller  diam- 
eter. The  kiln  should  be  not  less  than  30  feet  high,  and  the  diameter 
may  be  calculated  with  regard  to  the  amount  of  lime  that  it  is 


266  BEET-SUGAR  MANUFACTURE. 

desired  to  produce.  It  is  obvious  that  the  zone  of  decomposition 
should  be  so  placed  that  the  hot  gases  drawn  off  will  be  sufficiently 
cooled  by  their  passing  through  the  limestone  above  it,  and,  at 
the  same  time,  this  upper  layer  will  receive  the  proper  amount  of 
pre-heating.  Particular  attention  must  be  paid  to  this  point  in  the 
case  of  the  Belgian  kiln,  in  which  the  decomposition-zone  some- 
times is  too  high  and  often  too  low.  In  the  same  way  it  is  neces- 
sary that  the  cooling- zone  below  should  be  deep  enough  to  have 
the  lime  cooled  down  sufficiently  at  the  time  of  its  removal  from 
the  kiln. 

The  jacket,  or  masonry  surrounding  the  kiln,  should  be  air- 
tight and  the  observation-holes,  through  which  pokers  may  be 
introduced  to  remove  lumps  of  lime  from  the  side  of  the  kiln,  must 
also  close  tightly,  so  that  the  outer  air  cannot  enter,  and  it  is  equally 
desirable  to  prevent  much  of  the  carbonic  acid  from  escaping 
into  the  air. 

It  is  well,  though  not  absolutely  necessaiy,  to  break  up  the 
limestone  into  small  pieces  of  uniform  size.  If  the  kiln  is  working 
with  considerable  activity  this  breaking  up  of  material  can  be 
omitted,  particularly  if  labor  is  high.  Under  no  circumstances 
should  the  limestone  waste  be  thrown  into  the  kiln,  because  the 
latter,  particularly  when  the  kiln  is  not  very  large  in  diameter, 
is  likely  to  cause  the  contents  of  the  kiln  to  settle  into  a  compact 
mass,  so  that  the  kiln  will  not  draw  well.  The  coke  that  is  put 
in  with  the  limestone  should  be  well  broken  up,  so  that  it  will  be 
actually  consumed  in  the  decomposition-zone  and  not  partly  in 
the  cooling-zone. 

Withdrawal  of  lime  from  the  kiln  should  be  at  not  too  long 
intervals,  preferably  once  every  four  hours.  Thereby  the  con- 
tents of  the  kiln  are  more  frequently  set  in  motion  and  the  lime 
does  not  remain  too  long  in  the  decomposition-zone,  so  that  there 
is  less  danger  of  its  becoming  "dead."  It  is  very  satisfactory 
to  remove  the  lime  continuously  by  means  of  a  mechanical  device 
similar  to  that  used  in  the  bonechar-burners.  The  sticking  of 
lime  to  the  lining  of  the  kiln  is  usually  caused  by  the  formation 
of  slag.  The  limestone  forms  an  irregular  arch  over  these  places, 


TIIK  LIME-KILNS.  207 

which  must  be  broken  up  by  long  pokers  introduced  through  the 
observation-holes.  Sometimes  the  pieces  of  rock  are  so  firmly 
united  that  it  requires  several  hours'  labor  to  bring  the  kiln  back 
to  a  satisfactory  condition. 

Immediately  after  the  lime  has  been  withdrawn  at  the  bottom, 
the  kiln  must  be  fed  at  the  top.  This  refilling  of  the  kiln  must 
take  place  as  quickly  as  possible,  because  during  this  time  the 
gas  becomes  mixed  with  more  or  less  air  which  is  sucked  in,  and 
in  this  way  the  carbonatation  takes  place  more  slowly  when  such 
gas  is  used.  The  limestone  and  coke  should  be  reduced  to  a  uni- 
form size.  Mechanical  contrivances  are  very  advantageous  for 
charging  kilns  with  limestone  and  coke  and  for  continuous  removal 
of  lime,  as  they  save  labor  and  make  the  working  of  the  kiln  more 
uniform,  likewise  relieving  the  workmen  of  the  heat  and  dust. 

Special  attention  should  be  paid  to  the  manner  of  charging 
kilns.  The  kiln  is  first  dried  out  for  several  days  by  a  slow  wood 
fire.  In  the  preliminary  firing,  the  space  next  the  fire  can  be 
filled  with  limestone  alone,  this  being  mixed  with  coke  higher  up. 
Preliminary  firing  is  started  slowly  and  pushed  only  after  the 
masonry  is  warmed  sufficiently.  After  24  hours,  you  can  begin 
to  take  the  lower  layers  of  stone  out,  and  after  48  hours,  good  lime 
can  be  drawn  if  the  pumps  work  well. 

In  the  Belgian  oven  a  base  of  limestone  is  first  built  up  to  the 
discharge  openings  and  shavings  or  brush  and  wood  chopped  fine 
thrown  over  this  to  a  depth  of  from  three  to  six  feet,  and  then  a 
layer  of  coke.  Above  this  is  started  the  regular  charge  of  lime- 
stone and  coke  in  proper  proportion :  (10-12  :  1).  It  is  advisable 
to  use  somewhat  more  coke  for  the  lower  layers  and  at  first  not  to 
fill  the  kiln  entirely  full.  After  the  wood  is  kindled  and  the  fire 
come  up  so  that  the  limestone  is  red  hot,  the  gas  pump  is  started 
and  the  kiln  wholly  filled.  The  drawings  are  now  begun,  at  first 
somewhat  less  than  the  usual  size,  and  working  thus  in  two  days 
after  firing  well  burnt  lime  and  a  rich  saturation  gas  are  obtained. 

The  carbonic-acid  gas  from  the  kiln  contains  the  gases  of  com- 
bustion and  the  carbonic  acid  from  the  decomposition  of  the  lime- 
stone mixed  with  more  or  less  soot  from  the  fuel.  The  gas  on 


268  BEET-SUGAR  MANUFACTURE. 

leaving  the  kiln  has  a  temperature  depending  upon  the  height  of 
the  kiln,  but  this  temperature  should  never  rise  so  high  that  the 
exit-pipes  become  red  hot.  Before  the  gas  can  be  used  for  car- 
bonatation  purposes  it  must  be  cooled  and  freed  from  objectionable 
impurities.  For  this  purpose  a  mechanical  purification  by  means 
of  a  washer  ("  Laveure  ")  is  sufficient,  for  the  gases  other  than 
carbonic  acid  that  are  present,  such  as  oxygen,  carbon  monoxide, 
nitrogen,  and  sulphurous  acid,  do  not  exert  any  unfavorable  action 
upon  the  juices;  sulphurous  acid,  in  fact,  has  an  action  very 
similar  to  the  carbonic  acid  itself.  Such  constituents  of  the  gas, 
therefore,  need  not  be  removed.  When  there  is  not  enough  air 
introduced  into  the  kiln  there  is  more  or  less  sulphuretted  hydrogen 
formed  which  has  an  objectionable  effect  upon  the  juice;  the 
formation  of  this  gas,  however,  may  be  entirely  prevented  if  the 
proper  attention  is  paid  to  the  kiln  during  the  lime-burning  by  not 
allowing  the  reducing-zone  to  become  too  large  and  not  letting  the 
coke  that  is  thrown  pile  up.  Hence  there  is  no  particular  need  to 
attempt  to  remove  sulphuretted  hydrogen. 

The  gas-washers  serve  not  only  to  cool  the  gas  but  to  free  it 
from  cinders,  and  the  distillation  products  of  the  coal.  They 
consist  of  cylindrical  reservoirs  made  of  iron,  wood,  or  cement. 
Since  the  iron  is  often  strongly  attacked  when  there  is  an  insuf- 
ficient amount  of  water  in  the  washer,  wooden  or  cement  vessels  are 
usually  preferred.  Washing  is  best  effected  when  it  is  conducted 
on  the  principle  of  counter-currents,  by  allowing  the  water  to  cir- 
culate in  the  opposite  direction  to  the  gas  which  enters  at  the  top 
of  the  washer,  and  by  using  a  suitable  distributing  material  such 
as  coke.  Water  should  always  be  allowed  to  settle  at  the  lower 
part  of  the  tank  by  placing  the  overflow  about  sixteen  inches 
above  the  bottom,  so  that  the  hot  gases  on  entering  the  washer  at 
the  bottom  first  pass  through  this  layer  of  still  water.  As  water 
absorbs  carbonic  acid  the  amount  used  for  washing  should  be 
kept  as  small  as  possible;  the  inflow  of  water  is  regulated  so  that 
it  will  always  run  off  hot  at  the  overflow  to  gain  a  further  advantage 
that  hot  water  absorbs  much  less  gas  than  does  cold  water.  Even 
then  the  gases  are  well  cooled,  because  they  always  come  in  contact 


THE  LIME-KILNS.  209 

with  the  cold  water  in  the  upper  portions  of  the  washer.  When 
the  gases  are  well  cooled  the  gas-pump  becomes  more  efficient, 
because  the  cooler  the  gas  the  smaller  its  volume. 

The  efficiency  of  the  gas-pump  is  also  increased  by  making 
the  friction  in  the  washer  and  in  the  piping  as  small  as  possible. 
The  suction-pipes,  particularly  the  one  that  carries  hot  gases  from 
the  lime-kiln  to  the  washer,  should,  therefore,  be  large  in  diameter, 
and,  also,  when  the  gases  reach  the  water  they  should  not  be  obliged 
to  overcome  the  pressure  of  a  very  high  column  of  water.  The 
total  reduction  of  gas-pressure  in  the  piping  before  the  pump 
is  reached  should  not  be  more  than  that  corresponding  to  a 
column  of  water  three  feet  high.  In  order  to  control  this  reduc- 
tion of  pressure  it  is  advisable  to  insert  in  the  piping  in  front 
and  behind  each  washer,  as  well  as  at  the  pump  itself,  vertical 
glass  tubes  which  dip  into  water  at  the  bottom.  These  tubes  show 
the  vacuum  at  the  different  places,  and  in  this  way  the  loss  in 
pressure  at  the  different  pipes  and  in  the  washer  can  be  determined 
readily.  If  the  water  oscillates  up  and  down  in  the  tubes  to  any 
considerable  extent  it  indicates  irregular  washing.  In  order  to 
prevent  any  of  the  water  which  has  been  carried  along  from  the 
washer  from  getting  into  the  pump  it  is  well  to  place  a  water-trap 
in  the  piping.  It  is  not  feasible  to  pump  hot  or  dry  gases  owing  to 
the  excessive  lubrication  of  the  pump-cylinders  necessary.  The 
trace  of  dust  which  remains  in  the  gas  even  after  washing  forms 
a  greasy  substance  with  oil  which  hardens  after  a  while  and  inter- 
feres with  the  working  of  the  pump,  and  makes  other  troubles. 
Hence,  the  gas  is  best  pumped  moist,  or  is  moistened  in  the  punip- 
cylinder  by  water  which  also  serves  as  a  lubricant;  so  oil  is  not 
needed. 

Saturation  or  carbonatation  gas  is  richer  in  carbonic  add  when 
limestone  is  burned  with  a  small  amount  of  fuel  and  with  but  a 
slight  excess  of  air.  In  the  most  favorable  conditions,  when  the 
limestone  has  been  completely  burned  with  10  per  cent,  of  coke, 
it  is  possible  to  draw  off  from  the  kiln  a  gas  containing  37  per 
cent,  by  volume  of  carbonic  acid,  while  with  a  consumption  of 
12  per  cent,  of  coke,  and  under  otherwise  perfectly  similar  con- 


270  BEET-SUGAR    MANUFACTURE. 

ditions,  the  gas  will  only  contain  35  per  cent,  of  carbonic  acid. 
In  many  lime-kilns  the  gases  contain  from  30  to  35  per  cent,  of 
carbonic  acid,  but  this  percentage  fluctuates  because  the  production 
of  the  gas  is,  of  course,  greater  shortly  after  the  charging  of  a  kiln 
than  it  is  later.  As  a  rule  when  the  gas  contains  from  25  to  30  per 
cent,  of  carbonic-acid  gas  it  is  considered  satisfactory,  and  this  is 
usually  obtained  with  generator-burners.  In  fact,  many  people 
hold  that  the  carbonatation  requires  more  time  when  the  gas  con- 
tains more  than  25  to  30  per  cent.  If  this  is  known  to  be  the  case 
from  practical  experience  (although  it  is  scarcely  probable  theo- 
retically) it  is  not  advisable  to  diminish  the  efficiency  of  the  kiln  by 
introducing  more  air  into  it,  but  rather  the  gas  should  be  diluted 
with  air  through  a  valve  before  it  enters  the  carbonatation-tanks. 

SUPPLEMENT. 

Sulphurous  acid,  which  is  also  used  similarly  to  carbonic  acid 
in  the  carbonatation  process,  is  either  produced  by  burning  sulphur 
in  appropriately  constructed  ovens  or  it  is  purchased  in  a  liquid 
state  contained  in  iron  cylinders. 

Liquid  sulphurous  acid  is  somewhat  more  expensive  to  buy 
than  it  is  to  make  the  gas  at  the  factory,  although  in  some  respects 
it  is  rather  more  satisfactory,  especially  when  not  very  much  of  it 
is  to  be  used  and  it  is  desired  to  carefully  regulate  the  amount. 
If  a  stream  of  cold  water  is  allowed  to  flow  over  the  cylinder  con- 
taining the  liquid  sulphurous  acid  the  water  will  then  impart  to  the 
sulphurous  acid  sufficient  heat  to  convert  it  into  the  gaseous  con- 
dition. The  sulphurous  acid  thus  always  has  about  the  same 
temperature  and  pressure,  being  at  15°  to  20°  (59°-68°  F.),  about 
three  atmospheres  (45  Ibs.) ;  and  so  opening  the  valve  introduces 
a  uniform  amount  into  the  juice.  In  order  to  prevent  any  of 
the  juice  getting  into  the  sulphurous-acid  container  when  it 
becomes  empty,  and  consequently  exerts  no  more  pressure,  a 
check-valve  is  placed  in  the  piping. 

Sulphurous-acid  gas  produced  by  burning  of  sulphur  varies 
greatly  in  its  percentage  composition,  according  to  the  completeness 


THi:    LIME-KILNS.  271 

with  which  the  burning  of  the  sulphur  has  been  accomplished,  so 
that  more  attention  is  required  in  using  this  gas  in  the  carbonata- 
tion-tanks.  The  sulphur-burners  must  be  arranged  so  that  there 
is  no  danger  to  workmen  in  charging  the  burner,  and  so  that  no 
sulphur  will  sublime  into  the  pipes  and  possibly  get  into  the  juices; 
in  the  one  case  the  pipes  are  likely  to  become  choked,  while  in  the 
other  the  quality  of  the  juices  in  injuriously  effected.  These 
burners  are  built  in  various  ways  according  as  the  air  is  pumped  in 
or  the  gases  sucked  out.  In  the  first  arrangement  the  burners  are 
closed  air-tight  and  fitted  with  a  cooling-jacket.  The  air  necessary 
for  the  burning  is  forced  in  by  pumps,  or,  less  advisable  by  steam 
siphons,  these  being  regulated  according  to  the  supply  of  sulphurous 
acid  desired. 

When  the  gases  are  sucked,  the  juice  itself  is  used  as  the 
means  by  being  drawn  continually  out  of  the  bottom  of  the  col- 
lecting tank  by  a  centrifugal  pump  and  pumped  back  again  to  the 
tank  through  a  jet  apparatus,  this  latter  by  the  action  of  the 
juice  stream  sucking  the  gases  out  of  the  sulphur-burner.  Such 
burners  are  very  simple  affairs,  iron  boxes  open  at  one  end  where 
the  sulphur  is  burnt  in  a  pan.  Special  cooling  arrangements  are 
unnecessary,  since  the  air  draught  can  be  in  excess  and  do  the 
cooling. 


r  CHAPTER  XXV. 
HEAT-LOSSES  DURING  THE  PROCESS. 

PROPER  conditions  for  determining  an  exact  heat-balance 
are  lacking  in  the  sugar-factory,  and  it  is  hardly  to  be  expected 
that  it  would  be  possible  to  establish  such  under  the  variable 
prevailing  conditions.  At  the  same  time  it  is  of  great  impor- 
tance to  be  able  to  draw  some  conclusion  as  to  the  amount  of 
unused  heat  relative  to  the  total  generated  in  the  boilers,  for  in 
a  sugar-factory  steam  is  used  more  as  a  vehicle  of  transporting 
heat  rather  than  for  production  of  power.  The  amount  of  heat 
utilized  for  mechanical  work  amounts  to  only  about  one  or  two  per 
cent,  of  that  contained  in  the  amount  of  steam  produced;  after 
deducting  this  amount,  which  accomplishes  work,  the  heating- 
value  of  the  coal  burned  under  the  boilers  must  be  found  in  the 
heat  that  escapes  from  the  factory  or  is  given  up  during  the  process, 
for  there  is  no  heat-loss  in  the  different  heating-  and  evaporating- 
apparatus,  except  in  so  far  as  it  is  lost  with  regard  to  its  utilization 
in  the  factory. 

These  heat-losses  may  be  of  three  kinds: 

1.  Heat-losses  in  the  boiler-house. 

2.  Heat-losses  in  the  steam  while  on  its  way  from  the  boilers 
to  the  place  where  it  is  condensed. 

3.  Other  heat-losses. 

The  balancing  of  the  heat  can  only  be  carried  out  in  the  first 
two  cases  with  any  degree  of  accuracy. 

Heat-losses  in  the  Boiler-house. — An  amount  of  heat  is  pro- 
duced corresponding  to  from  60  to  75  per  cent,  of  the  caloric  value 

of  the  coal,  the  balance  being  lost  in  the  flue-gases  and  by  radiation. 

272 


HEAT-LOSSES  DURING  THE  PROCESS.  273 

The  heat-losses  which  take  place  here  can  be  ascertained  with 
accuracy  according  to  the  well-known  methods. 

Heat-losses  in  the  Steam. — The  steam  produced  in  the  boilers 
is  sent  partly  directly  and  partly  through  the  steam-cylinders  of 
the  engine  to  the  different  apparatus  where  it  is  to  find  further 
utilization.  On  the  way,  there  are  two  sources  of  heat-losses: 
those  due  to  radiation  and  heat  given  up  to  the  walls  of  the  steam- 
pipes,  and  heat  which  accomplishes  work  in  the  engines. 

The  amount  of  heat  lost  by  cooling  in  the  steam-pipes  depends 
upon  a  number  of  different  factors,  but  principally  upon  the  length 
of  piping  and  the  difference  in  temperature  between  the  steam  and 
the  outer  air.  These  losses  are  lessened  by  shortening  the  piping 
and  simplifying  it  as  much  as  possible,  and  by  covering  the  pipes 
with  some  good  non-conducting  material.  Superheating  the  steam 
also  acts  favorably  in  this  respect ;  for  superheated  steam,  although 
the  difference  in  temperature  between  it  and  the  outer  air  is  greater, 
gives  up  less  heat  to  the  walls  of  the  pipes  than  ordinary  wet 
steam.  Superheated  steam,  as  long  as  it  remains  superheated, 
behaves  like  hot  air  and  is  a  poor  conductor  of  heat. 

In  the  cylinders  of  the  steam-engines  which  are  partly  un- 
covered, there  is  more  heat  lost  per  unit  of  surface  than  in  well- 
covered  pipes.  The  continuous  whirling  motion  of  the  steam  in 
the  cylinders  also  tends  to  increase  the  heat-losses. 

The  heat  used  up  in  accomplishing  external  mechanical  work 
in  the  engines,  and  not  for  the  power  strictly  speaking,  but  rather 
for  the  overcoming  of  friction,  can  be  calculated  from  the  heat 
laws,  for  424  meter-kilograms  require  one  unit  of  heat.  For  the 
production  of  one  horse-power  about  1.18  kilograms  of  steam  are 
condensed  in  the  steam-cylinders  during  one  hour,  and  an  amount 
of  heat  corresponding  to  this  is  taken  from  the  steam. 

Besides  this  mechanical  work,  the  steam  does  other  work, 
chiefly  in  expanding  on  entering  the  steam-cylinders,  upon  the 
pressure  side  of  the  piston,  and  on  its  exit  upon  the  change  of 
stroke.  There  is  no  heat-loss,  however,  in  accomplishing  this 
work,  for  the  amount  of  heat  which  does  work  at  one  place  is  in 
another  transformed  into  heat  again.  After  deducting  the  amount 


274  BEET-SUGAR  MANUFACTURE. 

of  heat  lost  by  cooling  and  by  mechanical  work,  all  the  rest  of  the 
heat  which  enters  the  steam-cylinder  is  carried  in  the  exhaust  steam. 

It  has  been  established  by  means  of  experiment  that,  in  fac- 
tories where  there  are  a  considerable  number  of  engines  and  the 
piping  is  correspondingly  long,  there  is  about  15  per  cent,  of 
the  heat,  in  the  steam  which  passes  through  the  engines,  either 
lost  or  utilized.  Of  this  amount  3J  per  cent,  is  required  to  ac- 
complish work,  2  per  cent  is  lost  by  cooling  in  the  steam-cylinders, 
and  the  remaining  10  per  cent  or  so  is  lost  by  cooling  in  the 
direct  and  exhaust  steam-pipes. 

The  heat-losses  in  the  steam,  which  is  directly  transported  to 
the  place  where  it  is  to  be  used  for  heating,  are  naturally  much 
smaller  than  the  above;  for  this  steam  only  suffers  cooling  losses 
in  the  direct-steam  piping,  which  is  shorter  than  in  the  other  case. 
This  can  be  estimated  as  5  per  cent,  of  the  heat  contained  in  this 
steam. 

If  it  be  assumed  that  half  of  the  boiler-steam  passes  through 
the  engines  when  ordinary  high-pressure  engines  are  used,  and  the 
other  half  is  carried  directly  to  the  evaporating-pans,  etc.,  the 
amount  of  heat  lost  in  the  steam,  on  its  way  to  the  place 
where  it  is  going  to  be  utilized,  is  about  10  per  cent,  of  the 
heat  taken  up  in  the  boiler,  assuming  the  case  of  a  factory 
arranged  in  the  usual  manner  with  a  considerable  network  of 
piping. 

In  order  to  diminish  this  high  heat-loss,  a  number  of  different 
expedients  have  been  tried,  but  in  all  cases  a  careful  investigation 
should  be  made  as  to  whether  there  is  any  gain  accomplished, 
and  whether  it  is  a  pecuniary  gain. 

The  most  frequent  expedient  is  to  replace  the  ordinary  high- 
pressure  engines  with  modern  expansion  engines.  From  the 
explanation  given  above,  it  is  evident  that  such  a  change,  unless 
accompanied  by  other  changes,  cannot  of  itself  accomplish  any 
diminution  in  the  heat-losses,  because  the  amount  of  work  done 
in  each  engine  must  be  the  same  and  equal  quantities  of  heat 
will  be  used  up.  There  is  an  advantage  to  be  gained  in  the  in- 


HEAT-LOSSES  DURING  THE  PROCESS.  275 

stallation  of  modern  engines  only  when  the  cooling-losses  are 
diminished  This  can  be  accomplished  by  shortening  and  sim- 
plifying the  piping  as  much  as  possible,  and  replacing  several 
rimall  engines  by  one  large  one.  Whether  it  is  economical  to  make 
such  centralization  of  the  engine  work  depends  upon  the  con- 
ditions in  the  factory.  In  equipping  a  new  factory,  it  is  to  be 
expected  that  there  will  be  a  certain  amount  of  centralization,  at 
least  with  engines  having  up-to-date  expansion  fittings,  in 
order  to  make  as  short  and  simple  a  system  of  piping  as 
possible.  On  the  other  hand,  it  is  not  advisable  to  use  a 
single  engine  for  all  the  machinery  and  pumps,  transmitting 
the  power  by  belts  or  electricity,  not  only  on  account  of 
increased  expense,  but  also  because,  in  case  anything  hap- 
pens to  this  one  engine,  the  whole  work  of  the  factory 
will  be  interrupted. 

In  fact,  certainty  of  keeping  the  house  working  is  one  of  the 
chief  considerations  in  the  conduct  of  a  sugar-factory.  Every 
disturbance  causing  temporary  stopping  of  work  will  always  result 
in  increasing  expense  and  lengthening  the  campaign,  as  well  as  a 
certain  amount  of  sugar-losses.  A  factory  whose  machinery  is 
not  perfect,  but  is  such  that  the  work  goes  on  uninterruptedly 
with  all  engines  and  apparatus  working,  will  always  give  better 
results  in  the  long  run  than  one  more  modern,  but  which  cannot 
be  utilized  to  the  best  economy  on  account  of  causing 
stoppages. 

In  factories  already  constructed,  it  is  not  advisable  to  replace 
old  machinery,  that  is  capable  of  doing  steady  work,  by  new 
machinery,  except  when  there  is  too  much  exhaust  steam,  and 
this  steam  cannot  be  utilized  to  advantage  for  evaporating.  In 
such  cases  there  should  be  a  certain  amount  of  centralization  by 
replacing  several  of  the  older  engines  by  a  larger  and  more  modern 
one,  and  by  operating  as  many  pumps  as  possible  by  one  steam 
cylinder.  Above  all  else,  however,  the  attempt  should  be  made 
to  lessen  the  consumption  of  steam  by  adjusting  the  old  engines 
and  keeping  them  in  as  good  repair  as  the  better  types,  the  valve 


276  BEET-SUGAR    MANUFACTURE. 

surfaces  being  well  ground,  the  eccentrics  properly  adjusted,  the 
piston  made  tight,  and  the  engine  tested  from  time  to  time  by  an 
indicator. 

As  has  been  shown  above,  relatively  large  amounts  of  exhaust 
steam  can  be  used  to  advantage  in  the  evaporation  of  juice  if  it  is 
properly  connected  with  the  heating  and  evaporating  apparatus, 
provided  the  exhaust  has  a  pressure  of  about  three-fourths  of  an 
atmosphere  (10-12  Ibs.).  In  factories  in  which  there  is  a  large 
amount  of  this  exhaust,  it  is  sometimes  preferable  to  use  a  triple 
effect  rather  than  a  quadruple  effect,  if  the  exhaust  steam  only  is 
used  for  heating  and  boiling;  at  all  events  it  is  possible,  without 
going  to  much  expense,  to  arrange  so  that  the  consumption  of  coal 
will  be  kept  within  reasonable  limits. 

It  must  always  be  borne  in  mind  that  changing  the  equipment 
at  one  part  of  the  factory  will  usually  make  it  necessary  to  make 
some  changes  in  the  other  parts  as  a  necessary  consequence;  if  best 
results  are  to  be  obtained.  Thus,  when  there  is  a  centralization  of 
the  engine  work  it  is  usually  necessary  to  change  the  conditions 
in  the  boiler-house,  and,  in  consequence  of  the  considerable  lessen- 
ing of  the  amount  of  exhaust,  it  is  necessary  to  make  some  changes 
at  the  evaporating-pans,  so  that  the  cost  of  installation  of  the  new 
engine  is  increased  to  a  considerable  extent. 

It  is  almost  self-evident  that  it  is  not  only  unsuitable,  but  a 
waste  of  money,  to  connect  expansion  and  compound  engines  with 
condensers  in  a  sugar-factory ;  for  in  such  engines  none  of  the  heat 
can  then  be  utilized  for  evaporation  purposes,  so  that  heat-losses 
are  very  much  greater  than  in  the  old  and  ordinary  sorts  of 
engines. 

The  use  of  superheated  steam  for  driving  the  engines,  although 
it  has  been  used  to  great  advantage  in  other  industries,  and  produces 
an  equal  amount  of  work  with  less  steam,  is  in  this  respect  less 
useful  for  the  sugar-factory,  except  under  particular  conditions, 
namely,  when  the  exhaust  steam  is  present  in  too  great  a  quantity, 
and  must  be  diminished  in  amount.  But,  since  there  is  never  an 
excess  of  exhaust  steam  in  a  modern  sugar-factory,  it  follows  that 


HEAT-LOSSES   DURING  THE   PROCESS.  277 

the  superheating,  as  a  means  for  economizing  steam  in  the  produc- 
tion of  power,  has  no  utility  in  the  sugar-factory. 

It  is  unquestionable,  however,  that  the  superheating  of  the 
steam  is,  as  has  already  been  shown,  of  considerable  practical  im- 
portance in  lessening  condensation  losses  in  pipes  and  steam-cylin- 
ders. The  greatest  advantage,  then,  is  to  be  gained  when  the  heat 
of  the  waste  gases  from  the  boiler  are  used  for  this  superheating; 
their  usual  temperature  of  250°  to  300°  C.  (475°  to  565°  F.)  is  too 
low  to  accomplish  much  superheating.  This  has  led  to  use  of  special 
superheating  apparatus  behind  the  boiler  tubes,  where  the  gases 
have  a  temperature  of  500°-600°  (900°-1100°  F.),  or  to  heat  the 
steam  directly.  Of  course,  in  such  cases  heat  is  withdrawn 
from  the  boilers  or  from  the  fuel  directly,  and  their  evapora- 
tion efficiency  is  lowered  somewhat.  The  advantage  of  super- 
heating is  greater  in  proportion  as  the  steam  is  wet  as  it  comes 
from  the  boilers  in  condition  for  revaporizing.  Superheaters 
are  advisable  particularly  for  boilers  for  which  great  claims 
are  made. 

Up  to  the  present  time,  there  are  no  figures  available  to  show 
the  advantage  to  be  gained  in  superheating  steam  to  prevent  cooling 
losses.  The  need  of  such  figures  is  very  apparent,  because  the 
expense  of  installing  such  superheating  arrangements  is  no  small 
matter.  Further,  it  should  not  be  forgotten  that,  during  the  long 
season  when  the  factory  is  not  working,  the  superheating  appa- 
ratus will  suffer  more  from  rust  than  the  steam-boilers  and  tend 
to  become  leaky.  Consequently  the  cost  of  repairs  must,  in  the 
course  of  time,  amount  to  considerable. 

With  regard  to  the  working  of  the  engines  themselves,  the  use 
of  superheated  steam  offers  certain  disavantages  as  well  as  ad- 
vantages which  should  be  considered.  The  steam-cylinders  must 
be  much  more  strongly  lubricated,  and  with  a  viscous  and  more 
expensive  oil,  than  when  wet  steam  is  used,  in  which  the  water 
aids  in  the  lubrication.  Finally,  the  older  types  of  engines  are  not 
suited  for  the  use  of  superheated  steam. 

It  might  be  mentioned  again  that  it  is  only  steam  used  for  the 


278  BEET-SUGAR    MANUFACTURE. 

engines,  and  not  that  used  in  the  vacuum-pans,  etc.,  that  can  be 
superheated. 

Other  Heat-losses. — The  heat  contained  in  the  steam  or  other 
medium  carrying  heat  (hot  water,  juice)  can  only  be  utilized  when 
it  has  a  sufficiently  high  temperature. 

Every  time  heat  is  utilized,  or,  in  other  words,  in  every  trans- 
ference of  heat  from  one  medium  to  another,  there  is  a  lowering  of 
temperature,  and  the  repeated  utilization  in  the  multiple  effects 
consists  only  in  properly  distributing  this  fall  in  temperature. 
When  a  certain  lower  limit  of  temperature  is  reached,  it  is  no  longer 
possible  to  practically  utilize  the  heat  energy;  in  the  sugar-factory 
this  temperature  is  70°  C.  (158°  F.)  for  the  evaporation  and  50° 
to  60°  C.  (122°-140°  F.)  for  heating.  In  the  last  case  only  a  very 
small  portion  of  the  heat  can  be  utilized,  and  only  juices  and  water 
which  are  at  lower  temperatures  can  be  heated,  and  such  are  at 
hand  only  in  limited  amounts. 

Whether  it  is  advantageous  or  practical  to  use  heat  at  a  lower 
temperature,  in  engines  using  cold  steam  for  the  production  of 
power,  seems  at  present  to  be  questionable. 

All  the  heat  which  has  reached  the  lower  temperature  can, 
therefore,  be  regarded  as  useful  only  for  heating  purposes.  This 
heat  is  found  in  the  waste  waters  and  waste  products  of  the  factory, 
and  the  amount  of  this  heat  can  be  estimated  sufficiently  accurately, 
because  the  temperature  and  weights  of  these  products  are  easy 
to  determine. 

The  amount  of  heat  which  is  lost  during  the  cooling  in  the 
different  apparatus,  pans,  tanks,  piping,  juices,  water,  etc.,  cannot 
be  estimated  directly,  and  especially  that  portion  of  the  heat 
energy  which  is  contained  in  the  vapors  that  escape  during  car- 
bonatation,  the  boiling-down  of  the  juice,  the  steaming-out  of  the 
apparatus  and  centrifugals,  and  by  leakage. 

An  approximate  calculation  (see  Appendix  II)  is  obtained  by 
considering  that  of  the  amount  of  heat  which  remains  after  de- 
ducting the  heat-losses  in  the  steam-pipes  and  engines;  about 
two-thirds  is  lost  in  the  waste  products  from  the  diffusers  and 


HEAT-LOSSES*  DURING  THE  PROCESS.  279 

filter-presses,  and  in  the  excess  of  condensed  steam,  while  tne 
remaining  third  is  lost  in  amounts  which  cannot  be  determined 
directly. 

The  importance  of  diminishing  losses  by  cooling,  and  losses  due 
to  escape  of  steam,  becomes  clear  from  this  last  statement,  and  in 
it  is  the  key  to  economy  in  the  use  of  steam. 


CHAPTER  XXVI. 
FACTORY  CONTROL  AND  DETERMINATION  OF    SUGAR-LOSSES. 

IT  is  not  in  the  province  of  this  book  to  detail  the  principles 
and  methods  of  chemical  analysis  as  applied  to  factory  control,  but 
the  statement  cannot  be  made  too  emphatic  that  properly  con- 
ducted chemical  control  is  unquestionably  a  prime  requisite  for 
the  correct  and  profitable  conduct  of  the  work  of  a  sugar-factory. 
Unfortunately,  such  control  is  still  lacking  in  many. factories,  where, 
it  is  true,  in  daytime  the  testing  is  more  or  less  thorough,  but  at 
night  the  chemist  is  away,  and  often  not  even  average  samples  are 
taken  by  which  he  can  inform  himself  of  the  work  of  the  night. 

If  it  is  conceded  that  it  is  unquestionable  that  chemical  control 
is  necessary,  it  does  not  follow  that  it  is  the  sole  dependence  of  the 
manufacturer.  The  experienced  practical  man  at  once  detects 
anything  wrong  in  the  factory  by  the  behavior  and  appearance  of 
the  juice  and  other  products,  and  by  many  other  signs,  what  chemical 
investigation  shows  but  tardily.  Such  practised  observation  must 
always  characterize  the  man  who  has  supervision  of  the  factory 
routine.  No  irregularity  or  mistakes  in  working  with  liquors  or 
apparatus  escapes  the  vigilance  of  an  experienced  technical  man. 
Almost  always  there  are  many  obvious  tokens  which  indicate 
abnormal  work,  and  always  some  of  these  are  at  once  apparent  to 
the  superintendent.  The  results  of  chemical  control  depend  much 
on  the  accuracy  of  the  sampling,  and  it  can  happen  that  the  chemist 
discovers  an  irregularity  which  actually  does  not  occur  in  the  work, 
being  only  in  existence  in  a  faulty  sample.  On  the  other  hand, 
grave  mistakes  in  the  factory  quite  escape  chemical  detection  if 

no  sample  was  taken  at  such  particular  times,  especially  when  no 

280 


DETERMINATION  OF  SUGAR-LOSSES.  281 

systematic  average  sample  is  collected.  Mistakes  can  also  be  made 
in  special  analyses,  but  it  is  seldom  that  they  give  occasion  for  any 
considerable  error. 

The  field  of  activity  for  the  chemist  of  a  factory  is,  therefore, 
only  covered  to  a  small  extent  by  the  narrow  confines  of  the  labora- 
tory; so  far  as  he  has  any  time  available  he  should  be  in  the  factory 
seeing  the  general  samples  taken,  and  make  it  a  point  to  test  no 
sample  if  not  convinced  by  his  own  observation  that  it  was  prop- 
erly taken. 

Superintendents  and  chemists,  when  their  offices  are  not  united 
in  one  person,  should  work  hand  in  hand.  Any  unusual  happening 
in  the  factory  routine  must  be  at  once  explained  by  chemical  in- 
vestigation. Chemical  control  and  analyses  are,  it  is  true,  for  the 
special  purpose  of  finding  out  factory  mistakes,  but  their  chief  value 
is  to  determine  the  magnitude  of  the  error  and  the  means  for  its  abol- 
ishment. 

Laboratory  tests  which  are  designed  to  show  what  the  factory 
is  doing  or  to  explain  factory  troubles  must  be  well  planned  out 
and  conducted  with  every  care,  and,  above  all,  under  conditions 
imitating  as  closely  as  possible  those  actually  existing  in  the  factory. 
Otherwise  the  results  are  useless  for  practical  application  and  in- 
deed positively  mischievous,  as  they  lead  to  false  conclusions. 
Many  ideas  which  are  foreign  and  out  of  date,  and  even  some  that 
are  passed  around  by  practical  men  and  kept  alive  from  genera- 
tion to  generation,  owe  their  origin  to  investigations  erroneously 
carried  out  or  to  those  from  which  erroneous  conclusions  have 
been  drawn.  Often,  it  should  be  observed,  investigations  made 
with  beets  of  inferior  quality,  or  by  analytical  methods  no  longer 
recognized  as  exact,  have  been  used,  and  hence  for  the  condi- 
tions existing  to-day  they  have  no  scientific  value,  just  as  the 
conditions  as  known  to-day  may  have  as  little  relation  to  those 
which  may  control  the  industry  of  the  future. 

It  is  quite  wrong  to  attribute  factory  troubles  to  the  quality  of 
the  beets  without  investigating  further.  It  is  indeed  true  that 
beets  of  different  campaigns  and  at  different  periods  in  the  same 
campaign  are  apt  to  work  up  differently,  but  by  making  a  few 


282  BEET-SUGAR  MANUFACTURE. 

common-sense  changes  in  methods  to  suit  the  conditions,  almost 
any  beets  which  are  not  obviously  rotten  or  frozen  or  do  not  show 
extraordinary  damage  will  work  up  well,  or  at  least  work  up  so 
that  the  factory  can  run  to  its  full  capacity.  In  very  many  cases 
blame  for  factory  troubles  can  in  nowise  be  laid  to  the  beets,  but 
to  some  other  cause,  which  will  be  detected  quicker  if  the  habit  is 
broken  of  attributing  everything  to  the  beets.  At  the  beginning 
of  the  campaign  particularly,  troubles  occur  which  are  not  caused 
by  unripe  or  damaged  beets,  but  by  mistakes  of  inexperienced 
workmen,  such  as  are  at  first  not  readily  detected  by  superintend- 
ents till  they  themselves  again  get  in  practice  and  work  back  into 
the  fine  points  of  routine. 

Chemical  control  of  the  sugar-factory  has  its  chief  value  in  the 
determination  of  sugar-losses. 

The  difference  between  the  amount  of  sugar  in  the  beets  as 
shown  by  polarization  and  that  in  the  massecuite  or  in  the  sugar 
obtained  as  a  commercial  product  is  the  total  sugar-loss  in  manu- 
facture. If  the  determination  of  weights  and  polarizations  have 
been  worked  out  correctly  the  total  loss  is  usually  higher  than  the 
sum  of  those  losses  which  can  be  determined  in  waste-products,  and 
in  wash-  and  condensation  waters.  A  distinction  is  therefore  made 
between  determined  and  undetermined  losses,  or,  to  put  it  better, 
between  known  and  unknown  losses. 

To  determine  the  amount  of  sugar  going  into  the  factory  the 
beets  must  be  accurately  weighed  and  their  sugar-content  deter- 
mined in  good  average  representative  samples.  In  countries  where 
the  excise-tax  laws  do  not  compel  the  beets  to  be  weighed  it  is  often 
deemed  sufficient  to  obtain  this  weight  indirectly  from  the  number 
of  diffusion-cells  filled,  or  by  a  calculation  based  on  the  weight  of 
the  diffusion-juice  and  the  sugar-content  of  beets,  diffusion- juice, 
and  waste-products.  By  this  last  method  the  assumption  is  made 
that  the  undetermined  losses  do  not  occur  during  juice-extraction, 
so  that  the  sugar  obtained  in  the  juice,  together  with  that  deter- 
mined in  the  waste-products,  represents  the  sugar-content  of  the 
beets.  No  great  accuracy  can  be  claimed  for  this  way  of  calculat- 
ing, and  it  is  a  matter  of  surprise,  when  the  great  value  of  chemical 


DETERMINATION  OF  SUGAR-LOSSES.  283 

control  of  the  sugar-industry  is  recognized,  that  the  slight  expense  is 
not  incurred  to  meet  the  first  and  most  important  requirement 
for  such  control. 

Only  those  methods  for  the  determination  of  the  sugar- 
content  of  the  beet-slices  known  to  be  accurate  can  be  used,  namely, 
alcoholic  extraction,  which  must  be  controlled  by  extracting  a 
second  time,  or  the  hot-water-digestion  method  properly  carried 
out.  Although  by  these  methods  not  the  sucrose-content  but  the 
amount  of  polarizing  substances  is  given,  this  test  will  be  regarded 
as  scientifically  correct  till  it  becomes  possible  to  separate  the 
sucrose  from  the  other  optically  active  substances.  Especially  to 
be  rejected  are  those  methods  which,  designedly  or  not,  are  con- 
ducted with  less  care  and  so  give  lower  figures,  which,  while  possibly 
agreeing  better  with  the  results  of  factory  practice,  are  nevertheless 
false. 

Since  by  the  new  processes  of  working  up  massecuites  there  are 
no  longer  any  pure  first-product  massecuites,  the  sugar  obtained 
must  be  determined  from  the  weight  of  the  first-sugar  product  and 
the  volume  of  the  second  massecuite,  or,  if  this  is  also  worked  up 
with  a  grain  foundation  of  added  sugar,  from  the  weight  of  the 
finished  commerical  sugar  and  the  molasses.  The  more  the  sirups 
are  worked  up  during  the  campaign  the  greater  the  difficulty  in 
separating  them  to  reckon  the  weekly  yield.  Nevertheless,  some 
kind  of  a  separation  of  sirups  can  be  worked  out,  and  at  least 
several  times  during  the  campaign  a  determination  of  yields  and 
losses  should  be  made  with  as  great  accuracy  as  possible.  Small 
amounts  of  sirup  which  are  carried  over  in  the  account  from  week 
to  week  can  be  reckoned  as  massecuite.  There  is  no  difficulty  in 
taking  average  samples  of  sugar  or  sirup  massecuites. 

The  only  determinable  sugar-losses  are  those  occuring  in  the 
filter-press  scums  in  the  diffusion  work  and  the  loss  hi  the  condenser 
water,  for  these  are  the  only  losses  capable  of  measurement  and 
which  can  be  calculated  with  reasonable  accuracy  from  tests  of  the 
waste-products.  There  are  other  losses  of  which  we  have  positive 
knowledge,  but  whose  magnitude  cannot  be  quantitatively  meas- 
ured through  lack  of  all  data,  and  which,  therefore,  have  to  be 
reckoned  as  undeterminable. 


284  BEET-SUGAR  MANUFACTURE. 

To  this  class  of  undetermined  losses,  which  are  recognized,  but 
which  do  not  last  long  enough  at  one  time  to  permit  of  quantitative 
determination,  belong  especially  those  losses  which  are  due  to 
decomposition  of  sugar  in  evaporating  and  boiling,  losses  in  the 
filter-press  cloths,  and  mechanical  losses  caused  by  entrainment  of 
juice  or  sirup.  All  these  losses  taken  together  do  not,  however, 
reach  a  figure  of  much  magnitude,  and  at  most  are  reckoned  as 
a  few  hundredths  of  a  per  cent,  on  the  weight  of  the  beets,  assuming 
of  course  that  the  juices  are  normal  and  are  worked  up  alkaline, 
and  that  no  mechanical  loss  out  of  the  ordinary  has  occurred. 
Hence  these  losses  give  no  explanation  of  the  considerable  amount 
of  undetermined  loss  which  occurs  in  every  factory,  and  is  always 
found  however  careful  the  chemical  control.  The  greatest  vigilance 
and  care  are  necessary  in  determining  the  known  losses  accurately. 
If  the  tests  are  made  carelessly,  whether  in  sample  taking  or  in 
analysis,  the  losses  found,  both  total  and  known,  are  almost  in- 
variably too  small.  If  the  books  show  a  small  sugar-loss  it  is  not 
by  any  means  evidence  of  good  work.  On  the  contrary,  such  figures 
should  be  viewed  with  some  suspicion. 

As  is  well  known,  according  to  the  annual  reports  of  factories 
whose  technical  standing  is  recognized  as  good,  the  total  sugar- 
loss  is  given  as  1.0-1.5  per  cent,  of  the  beets,  of  which  0.5-0.7  per 
cent,  are  known  losses,  so  that  a  half  more  appear  as  unknown 
losses,  and  so  far  cannot  be  explained  as  being  losses  recognized 
but  undetermined.  While  it  is  unpleasant  for  a  superintendent 
to  contemplate  losses  as  great  as  these,  which  would  be  serious 
if  they  actually  did  represent  sugar,  it  certainly  is  still  more 
unsatisfactory  to  one  who  wishes  to  get  at  the  truth  of  prac- 
tical sugar  work.  It  is,  however,  almost  certain  that  these 
"losses"  are  not  sugar-losses,  but  errors  of  polarization,  although 
so  far  no  satisfactory  explanation  has  been  given  to  account 
for  them. 

The  sugar-losses  which  are  worth  consideration  are  only  those 
which  have  been  actually  determined,  and  it  may  be  better  in  some 
ways  to  report  only  these,  as  their  measurement  is  what  concerns 
the  technical  man.  The  total  loss  determination,  on  the  contrary, 


DETERMINATION    OF  SUGAR-LOSSES.  285 

gives  utterly  erroneous  ideas  of  the  actual  work,  and  may  be  looked 
upon  as  of  no  value. 

The  most  important  known  sugar-losses  occur  in  the  diffusion 
work,  especially  in  the  exhausted  slices  and  waste-water.     It  is 
very  difficult  to  collect  a  proper  average  sample  of  the  exhausted 
slices,  for  not  only  do  the  different  tanks  have  residues  at  different 
degrees  of  exhaustion,  but  slices  in  the  same  diffuser  vary  much  in 
their  sugar-content.     Further,  as  the  weight  of  the  wet  slices  is 
not  determined  directly,  and  the  adhering  water  varies  from  80  to 
100  per  cent.,  determinations  should  be  made  on  these  slices  merely 
for  control  of  the  diffusion,  the  sugar-loss  being  calculated  from 
tests  on  the  pressed  residues  and  on  the  press-water.     The  weight  of 
the  pressed  residues  can  be  determined  exactly  from  the  accounts 
of  the  farmers.     Good  average  samples  can  be  obtained  at  the  bins 
below  or  in  other  ways.     These  are  always  more  reliable  than  those 
taken  on  the  wet  slices,  as  this  residue  has  been  thoroughly  mixed 
in  passing  through  the  various  conveying  machinery,  such  as  bucket 
and  screw  elevators,  as  well  as  in  the  presses  themselves.     The  de- 
termination is  best  made  by  the  hot-digestion  method,  which  gives 
very  satisfactory  values  for  this  waste  product,  which  is  the  richest 
of  all  in  sugar.     Obviously,  good  average  samples  of  the  press  water 
can  be  obtained  very  easily,  especially  if  some  kind  of  dropping- 
apparatus  is  used  for  taking  samples.     The  weight  of  the  press- 
water,  which  will  hardly  exceed  10  per  cent,  on  the  beets  can  only 
be  estimated,  but,  as  its  sugar-content  is  relatively  small,  the 
error  is  of  no  consequence.     The  same  remarks  apply  to  the 
diffuser  waste-waters,  whose  amount  can  only  be  estimated  if  extra 
water  is  used  in  discharging  the  chips.     The  sugar-content  in  these 
waters  is,  however,  still  less  than  in  the  press-waters,  so  that  an 
exact  determination  of  the  amount  of  water  is  of  no  consequence, 
since  the  greatest  error  which  would  be  introduced  would  only 
affect  the  loss  determination  a  few  hundredths  of  a  per  cent,  on  the 
weight  of  the  beets.     In  diffusion  where  the  waste-waters  are 
worked  back  and  in  the  hot  mash  methods  there  is  obviously 
no  sugar  loss  if  the  sugar   collected    in  the  dry  by-product  is 
reckoned  as   recovered.     In   these   processes  care   need  only  be 


286  BEET-SUGAR  MANUFACTURE. 

taken    that    the    fodder    contains    only  so   much    sugar   as   is 
profitable. 

It  is  not  easy  to  take  good  average  samples  of  carbonatation- 
scums,  as  the  press-cake  of  different  filter-presses,  and,  indeed,  of 
the  same  press,  show  very  different  degrees  of  sweetening  off.  Sam- 
ples should  be  collected  when  the  press  is  discharged  by  taking 
portions  of  several  cakes  and  from  different  places  in  the  cake. 
The  surer  method  is  to  sample  from  the  scum-wagons  by  means  of 
a  trier.  When  the  scums  are  disposed  of  by  mixing  with  water 
to  a  thin  paste  very  good  average  samples  can  be  collected  easily, 
but,  of  course,  the  sugar  must  be  calculated  on  the  weight  of  the 
original  scum,  which  requires  a  determination  of  the  water-content 
or  the  specific  gravity  of  the  watery  mixture.  The  weight  of  the 
scums  is  usually  determined  from  the  number  of  presses  which 
have  been  discharged.  It  suffices,  however,  to  calculate  the  scums 
from  the  weight  of  lime  used,  as  they  can  be  taken  as  3.5  to  4  times 
the  weight  of  the  latter,  accordingly  as  they  are  dry  or  wet. 

Suitable  samples  can  be  collected  from  the  hot-well  waters  of 
the  condensers  by  means  of  accurate  drop-sampling  apparatus. 
The  amount  of  water  can  be  calculated  with  sufficient  exactness, 
if  its  temperature  is  known,  as  well  as  that  of  the  condensed  vapors 
and  the  injection-water. 

The  calculated  factory  losses  per  100  parts  of  beets,  in  a 
factory  using  ordinary  diffusion,  are  about  as  follows: 

Total  sugar-loss 1.20%  of  beets 

Of  which  are  known 

In  expressed  beet  residues  50%,  polarizing  0.50%  =  0.25% 

Press-water 40%  "         0.20%  =  0.08% 

Diffusion  waste- waters  130%  0 . 10%  =  0 . 13% 

Scums,  1st carbonatation  8%  "         1.5%   =0.12% 

Scums,  final         "  0.5%       "         4 . 0%  =  0 . 02% 

Hot- well  water 600%  "         0.00    =0.00 

Total  known  losses 0 . 60% 


Unknown  losses 0.60% 

In  factories  where  the  diffusion-juice  is  exactly  measured  the 
total  losses  in  juice  extraction  can  be  exactly  determined  if  cor- 
rect average  samples  are  collected.  As  this  juice  always  contains 


DETERMINATION'    OF  SUGAR-LOSSES.  287 

many  germs  which  quickly  decompose  sugar  the  samples  must 
never  stand  more  than  a  half  hour,  or  at  the  very  most  an  hour, 
without  addition  of  lead  acetate  or  mercuric  chloride.  Whether 
the  diffusion  process  is  responsible  for  greater  losses  not  yet  capable 
of  determination  is  a  much-discussed  question,  which  has  not  yet 
been  answered.  In  the  pressing,  as  in  the  diffusion  as  carried  out 
in  the  usual  manner  nowadays,  the  sugar  brought  in  in  the  beets 
will  be  found  again  in  raw  juice,  waste-waters  and  fodders.  Never- 
theless, the  sugar  which  is  contained  in  the  raw*  juice,  after  making 
deduction  for  losses  calculated  for  scums  and  waste  waters  will 
not  be  found  exactly  in  the  massecuite.  As  has  already  been 
stated,  what  is  the  cause  of  this  undetermined  loss,  which  amounts 
to  about  J  per  cent,  on  the  weight  of  the  beets,  is  not  at  all  clear. 

Among  the  losses  not  capable  of  determination  are  especially 
those  known  as  mechanical  losses,  caused  by  leaks  in  valves  or 
heating-coils,  as  well  as  those  due  to  carelessness  of  workmen.  It  is 
the  business  of  the  practical  factory  man  to  prevent  these  as  far  as 
possible.  Discharge-valves  which  are  leaky  or  not  properly  closed 
are  the  cause  of  juice-losses  in  the  diffusion.  Such  discharge-valves 
should  be  done  away  with  where  the  spurting  of  water  from  the 
lowrer  manholes  on  opening  the  diff users  can  be  prevented,  as  is 
possible  with  side  discharge  by  use  of  cloths.  The  space  under 
the  sieves  should  be  filled  with  hydraulic  cement,  leaving  only 
room  enough  for  the  flow  of  juice  between  the  sieve  and  the 
bottom,  or  otherwise  considerable  cold  water  collects  there  and 
later  on  dilutes  the  juice  when  the  diffuser  is  filled  with  fresh 
slices  for  mashing.  As  a  rule  the  later  forms  of  diffusion-plants 
have  discharge-valves  and  manholes  in  plain  view,  so  that  any  leak 
would  be  at  once  detected  and  loss  prevented.  Mechanical  juice- 
losses  can  also  occur  at  the  waste-valves  of  carbonatation-tanks 
and  evaporators  which  are  used  for  washing  out  on  Sundays. 
Such  valves  or  cocks  should  always  be  closed  by  the  superintendent 
or  his  representative  personally,  and  locked  to  prevent  any  im- 
proper use.  It  is  hardly  necessary  to  say  that  all  waste-pipes  and 
likewise  all  juice-pipes  should  be  so  placed  that  they  can  be  easily 
inspected. 

Losses  by  leaks  of  heating- tubes  or  -coils  in  evaporators  or 


2o8  BEET-SUGAR  MANUFACTURE. 

vacuum-pans  ought  not  to  escape  notice,  since  the  greater  part  of 
the  condensed  water  is  utilized  for  boiler-feed,  and  the  smallest 
amount  of  sugar  makes  itself  noticeable  by  the  odor  of  the  steam. 
Condensed  water  not  used  for  boiler-feed,  especially  that  from  the 
juice-heaters,  should  be  frequently  tested  for  sugar. 

If  these  simple  precepts  are  followed  no  mechanical  loss  can 
take  place  without  being  detected. 


CHAPTER  XXVII. 

GENERAL  SUGGESTIONS   CONCERNING    THE   EQUIPMENT   AND 
MAINTENANCE  OF  A  BEET-SUGAR  FACTORY. ' 

A  BEET-SUGAR  factory  is  one  which  prepares  from  a  natural  raw 
product  a  product  still  crude  but  greatly  improved.  It  is  only  in 
special  factories,  or  special  parts  of  the  same  factory,  that  this 
crude  product  is  made  over  into  a  product  ready  for  use.  There  is. 
therefore,  no  reason  for  aiming  at  any  beauty  in  buildings  or 
machinery,  as  is  to  some  extent  necessary  in  factories  built  for 
advertising  purposes.  The  chief  requisite  is  the  practicability  of 
the  arrangement  as  a  whole  and  the  individual  parts,  as  well  as 
economy.  Attractiveness,  such  as  a  beautiful  arrangement  of  the 
factory,  or  a  beautiful  engine-house,  costs  money,  without  aiding 
in  the  attainment  of  the  purposes  for  which  the  factory  is  built r 
which  is  to  produce  economically  from  beets  the  greatest  possible 
quantity  of  sugar  of  good  quality;  it  increases  cost  of  manufacture 
by  raising  the  costs  of  insurance  and  interest.  Such  sums  play  an 
important  part  in  the  conduct  of  a  beet -sugar  factory  in  which  it 
is  necessary  to  make  the  entire  year's  earnings  within  a  few 
months. 

With  regard  to  the  fittings  and  method  of  working  the  factory 
much  depends  upon  the  customs  levied  and  the  demands  of  com- 
merce. In  countries  in  which  there  is  a  tax  upon  the  weight  of  the 
beets  it  is  necessary  to  avoid  as  much  as  possible  all  losses  at  the 
different  stages  in  the  manufacture,  because  the  value  of  the  sugar 
is  greatly  increased  by  this  duty,  sometimes  giving  it  double  its 
original  value  or  more.  In  such  cases  the  number  of  diff users  and 
filter-presses  should  be  large.  On  the  other  hand,  when  there  is  a 

289 


290  BEET-SUGAR  MANUFACTURE. 

tax  levied  upon  the  juice  it  is  not  so  important  to  exhaust  the 
beet-chips  thoroughly,  but  more  stress  is  to  be  laid  upon  the  pro- 
duction of  a  juice  whose  temperature  and  purity  are  most  favor- 
able when  the  duty  is  considered.  It  is  also  necessary  in  this  case 
to  carefully  sweeten  off  the  scums  and  to  avoid  all  losses  caused  by 
the  mechanical  entrainment  of  sugar  with  the  steam,  but  these  are 
always  the  aims  of  the  sugar-manufacturer  in  every  sugar-factory. 
In  countries  where  there  is  a  sugar-tax  levied  upon  the  finished  prod- 
uct the  factory  cares  less  for  sugar-Losses  during  process  of  manu- 
facture. Of  course  the  sugar-losses  should  on  no  account  exceed 
a  reasonable  amount,  but  frequently  it  is  better  to  work  rapidly, 
and  prepare  a  good  product  rather  than  to  make  the  yield  greater 
and  the  product  poorer. 

The  demands  of  commerce,  or,  in  other  words,  the  market, 
regulates  the  quality  of  the  sugar  produced,  and  this  has  its  in- 
fluence upon  the  conduct  of  the  sugar-house.  When  an  alkaline 
product  is  desired  by  the  trade  it  is  necessary  to  regulate  the 
process  in  this  respect  from  the  defecation  onward. 

A  good  beet-sugar  factory  should  have  well-ventilated,  well- 
lighted  and  spacious  rooms  arranged  so  that  the  workings  of  the 
whole  factory  can  be  easily  watched  by  the  one  in  charge.  The 
requisite  cleanliness  should  be  easily  attained  and  the  machinery 
and  apparatus  should  be  good,  strong,  and  conveniently  arranged. 
As  to  whether  engines  and  apparatus  should  be  of  the  latest  pattern 
and  design  is  a  matter  of  more  or  less  indifference  to  the  practical 
sugar-man.  If  the  engines  furnish  the  requisite  power  without  an 
excess  of  steam  in  the  exhaust,  and  all  of  the  apparatus  is  properly 
arranged  and  capable  of  doing  the  work  expected,  they  fulfil 
their  purpose,  and  it  is  entirely  superfluous  to  make  any  other  de- 
mands in  this  respect.  The  duties  of  the  manager  of  the  factory 
cover  all  the  details  involved  in  the  manufacture  of  the  sugar,  and 
he  must  observe  everything  that  happens  to  the  beets  or  to  the 
juices,  suggesting  improvements  when  necessary.  This  takes  up 
pretty  much  all  of  one  man's  time,  so  that  the  care  and  working  of 
the  engines  and  machinery  should  be  left  to  the  engineer.  All 
irregularities  in  the  working  of  the  engines  or  machinery  which 


GENERAL  SUGGESTIONS  FOR  A  FACTORY.  291 

may  cause  trouble  in  the  process  should  be  looked  after  at  once, 
for  preventing  stoppages,  together  with  working  the  factory  up  to  its 
capacity,  are  the  chief  factors  towards  working  cheaply  and  well. 
Each  stoppage  involves  expense,  not  only  on  account  of  the  un- 
employed labor  and  waste  of  fuel,  but  also  because  the  purity  of 
the  juice  is  lowered  and  sugar-losses  are  greater  in  the  beets  that 
are  stored  for  a  longer  time. 

The  more  rapidly  juices  are  worked  up,  by  avoiding  all 
stoppages,  the  better  their,  quality.  They  suffer  especially  in 
slow  diffusion,  by  delays  in  carbonatating,  in  evaporating  and 
excessively  by  prolonged  boiling  in  vacuum  pans.  Their  worst 
characteristics  show  in  stickiness  and  dark  color  in  massecuites, 
in  poor  yield  and  difficult  purging.  It  is  always  wrong  to  have 
apparatus  too  large  at  any  stage  of  the  process.  When  this  is  the 
case,  either  the  apparatus  in  question  must  be  reduced  in  size,  or 
the  other  apparatus  increased  in  proportion,  so  that  the  capacity 
of  the  factory  will  be  changed.  When  the  size  of  the  apparatus  at 
any  point  is  increased  care  must  be  taken  to  make  sure  that  the 
new  capacity  corresponds  to  that  of  the  apparatus  at  the  other 
stages  of  the  process,  as  otherwise  it  will  be  necessary  to  make 
certain  changes  or  enlargements  annually.  The  size  of  different 
forms  of  apparatus  should  be  such  that  those  later  in  the  process 
have  a  slightly  greater  capacity  than  the  preceding,  or  at  least  it 
should  be  possible  to  make  the  increase  quickly.  This  is  partic- 
ularly true  of  any  transporting-apparatus  which  takes  product 
from  another.  Indeed,  transporting  and  transmission  machinery 
can  never  be  made  strong  enough ;  this  statement  ought  to  be  made 
most  emphatic  as  unfortunately  grievous  sins  are  too  often  com- 
mitted on  this  point.  A  fourfold  factor  of  safety  should  be  de- 
manded over  that  required  for  transporting  apparatus  in  other 
industries  for  equal  loads,  especially  for  beet  and  chip  carriers, 
owing  to  the  exceedingly  variable  conditions  of  their  use  and 
because  frequently,  when  the  work  is  pushed,  they  do  not  come 
up  to  the  capacity  shown  previously. 

Increasing  the  size  of  the  factory  is  usually  the  best  way  to 
reduce  the  cost  of  manufacture,  but  this  is  true  only  within  certain 


292  BEET-SUGAR  MANUFACTURE. 

limits.  If  a  factory  can  obtain  all  the  beets  needed  so  as  to  main- 
tain a  campaign  of  a  normal  duration,  increasing  the  capacity  of 
the  factory  should  stop  only  when  the  freight  charges  for  bringing 
beets  from  a  distance  more  than  compensates  any  gain  in  the 
economy  of  operating  the  factory.  It  may  then  be  more  advanta- 
geous to  build  a  new  factory  in  a  more  central  location.  If  a  factory 
cannot  obtain  more  beets  than  are  used  at  present,  increasing  the 
size  of  the  factory  will  result  simply  in  shortening  the  campaign. 
This  is  advantageous  up  to  a  certain  extent,  because  the  cost  of 
operating  will  be  somewhat  diminished,  and  it  will  not  be  necessary 
to  store  beets  at  all,  since  they  can  all  be  worked  up  at  the  time  of 
their  greatest  sugar-content.  If  the  duration  of  the  campaign  ha« 
been  reduced  co  about  six  weeks  then  increasing  the  capacity  of 
factory  will  be  not  only  unnecessary  but  even  injurious,  because 
it  may  happen  that  the  farmers  cannot  supply  the  beets  fast  enough 
in  the  shorter  period,  and,  consequently,  the  work  may  have  to  be 
stopped  on  account  of  their  insufficiency.  In  such  cases  it  is  better 
to  attempt  to  improve  the  process  and  to  increase  the  yield  by  care- 
Jul  work  rather  than  to  enlarge  the  factory. 

When  new  appliances  are  added  for  improving  process  the 
gain  should  be  quite  considerable.  In  most  cases  the  returns  should 
show  interest  upon  the  capital  invested  of  from  15  to  20  per  cent., 
because  every  year  new  discoveries  are  being  made  which  make 
the  apparatus  at  hand  become  more  or  less  out  of  date,  so  that  its 
value  decreases  rapidly.  Furthermore,  many  innovations  corre- 
spond to  the  prevailing  fashion  in  the  manufacture  of  apparatus 
or  the  price  may  be  set  altogether  too  high  by  advertising.  At  one 
time  a  number  of  improvements  will  be  suggested  with  regard  to 
the  diffusion,  at  another  time  it  will  be  the  defecation  that  is  im- 
proved, and  so  on  throughout  the  whole  process,  as  a  result  of 
fashion  to  some  extent.  Those  who  attempt  to  follow  all  these 
changes  will  soon  empty  their  purses  without  effecting  any  cor- 
responding gain.  Consequently  one  should  go  slow,  as  more  harm 
is  usually  done  by  changing  too  quickly,  and  frequently  the  actual 
advantages  to  be  obtained  from  an  invention  may  be  attained  in  a 


GENERAL  SUGGESTIONS  FOR  A  FACTORY.  293 

much  more  simple  manner.  If,  however,  the  advantages  of  a  new 
device  are  apparent  no  time  should  be  lost  in  adopting  it. 

For  careful,  work  great  cleanliness  should  be  maintained 
throughout  the  whole  factory,  but,  above  all  else,  the  work  itself 
and  the  inside  of  apparatus  should  be  clean.  Although  it  is 
advisable  to  keep  the  whole  factory  clean  it  is  not  wise  to  pay 
too  much  attention  to  exteriors,  for  it  is  in  the  different  vessels 
where  the  juice  is  contained  that  cleanliness  is  of  most  vital 
importance.  Those  which  otherwise  require  little  attention  con- 
tinually demand  care  in  this  regard. 

The  total  cost  of  operating  a  factory  is  naturally  very  different 
in  different  cases.  On  the  other  hand,  the  actual  expenses  in- 
curred during  the  campaign  are  only  slightly  different  in  the  vari- 
ous factories.  In  German  factories  the  expense  during  a  cam- 
paign was  found  to  be  per  100  Ibs.  of  beets:  wages,  1.15  c.  to  1.36  c,; 
fuel,  0.9  c.  to  1.15  c.;  Kme,  0.11  c.  to  0.34  c.;  press-cloths, 
0.45  c.  to  0.57  c.;  and  lubricants,  0.45  c.  to  0.57  c.  The  greater 
the  number  of  beets  worked  up  into  sugar  the  smaller  becomes  the 
cost  of  each  pound  of  sugar  produced.  In  Germany  it  costs  from 
six  to  ten  cents  to  work  up  100  Ibs.  of  beets,  allowance  being  made 
for  depreciation  in  the  value  of  the  plant,  repairs,  summer  work, 
etc.  It  is  always  hard  to  estimate  correctly  the  cost  of  manufac- 
turing sugar,  for  sometimes  small  factories  work  more  economically 
than  large  ones,  particularly  when  the  freight  on  beets  and  by- 
products is  taken  into  consideration. 

For  practical  control  of  the  factory  it  is  well  to  place  the  data 
of  the  working  at  each  part  of  the  factory  upon  a  blackboard,  or 
upon  a  chart,  so  that  a  very  good  idea  of  just  what  the  factory  is 
doing  may  be  obtained  by  simply  inspecting  these  items.  In  such 
cases  the  following  details  should  be  noted :  The  amount  of  beets 
used,  the  number  of  diff users  filled,  the  length  of  time  each  diffuser 
is  in  operation  and  the  time  of  discharging,  the  degree  Brix  of  the 
diff  user-juice  from  each  measuring-tank,  the  number  of  emptied 
presses,  the  number  of  defecating-  and  carbonatating-pans  in  opera- 
tion, the  density  of  the  thick  juice  that  is  drawn  off,  the  alkalinity 
of  the  juices,  the  beginning  and  end  of  each  boiling,  both  of  firsts 


294  BEET-SUGAR   MANUFACTURE. 

and  after-products,  the  time  of  stirring  and  temperature  in  the 
crystallizers,  the  number  and  contents  of  the  vessels  containing 
the  after-massecuites,  the  weight  of  the  centrifugated  sugar,  andr 
furthermore,  the  data  concerning  the  operation  of  the  boiler-house. 
Noting  all  these  details  helps  greatly  in  the  rapid  detection  of  mis- 
takes and  troubles  in  process. 

At  the  same  time  the  real  day-book  or  journal  of  the  factory 
should  not  be  forgotten.  This  should  contain  all  technical  data,  not 
alone  notes  taken  from  the  factory  working  and  extracts  from 
the  laboratory  book,  but  also  the  receipts  of  fuel,  limestone f 
lime,  filter-cloths,  acid,  lubricants,  etc.,  and  the  sugar-sacks,  the 
amount  of  beets  received  and  the  quantity  stored,  as  well  as  the 
storage,  deliver}',  and  examination  of  the  sugar.  These  results  are 
all  the  more  valuable  if  the  notes  are  taken  neatly  and  arranged  so 
that  the  data  are  easy  to  find.  It  is  not  easy  to  give  a  scheme  for 
tabulating  the  results  in  such  a  book,  because  the  conditions  vary 
so  much  in  the  different  factories. 

In  some  factories  samples  of  juices,  massecuites,  etc.,  are  taken 
at  regular  intervals,  and  the  results  are  shown  to  the  superin- 
tendent of  the  factory.  Although  this  practice  is,  on  the  whole, 
very  commendable,  the  results  are  sometimes  misleading  on  ac- 
count of  workmen  always  taking  favorable  samples.  It  is  well  to 
take  the  specimens  personally  when  possible,  and  not  leave  it  to 
workmen. 

A  very  important,  although  less  busy,  period  is  the  time  for 
making  repairs.  After  the  beets  have  all  been  worked  up  the 
machinery  and  apparatus  should  be  cleaned  immediately,  at  first 
somewhat  superficially,  and  later  very  thoroughly,  and  everything 
should  be  closely  examined  to  see  what  repairs  are  necessary. 
The  heavier  repairs  which  will  have  to  be  made  in  a  machine-shop 
should  be  made  early  in  the  spring,  for  the  mechanics  are  then 
not  very  busy  and  the  work  is  more  likely  to  be  done  carefully 
and  finished  on  time. 

Such  repairs  and  minor  improvements  as  can  be  carried  out  at  the 
sugar-house  should  be  divided  proportionately  through  the  whole  of 
the  period  that  the  factory  is  idle,  so  that  workmen  are  uniformly 


.GENERAL  SUGGESTIONS  FOR    A    FACTORY.  295 

busy  throughout  the  whole  of  the  summer.  Of  course,  it  is  ad- 
vantageous to  be  as  independent  as  possible,  and  it  is  best  for  the 
factory  to  make  all  the  repairs  it  can  on  the  spot. 

The  parts,  after  being  inspected  and  repaired,  are  immediately 
put  together  again.  They  should  be  kept  dry  and  covered  with 
grease  to  prevent  rust,  and  they  should  also  be  protected  from 
dust  by  suitable  coverings. 

In  case  of  doubt  as  to  whether  repairs  or  new  parts  are  neces- 
sary it  is  always  well  to  consider  what  the  effect  will  be  if  the  part 
gives  out  during  the  campaign:  does  the  whole  factory-work  de- 
pend upon  the  piece  of  machinery  in  question,  or  can  the  repairs 
be  made  during  the  campaign  without  stopping  the  regular  work? 
The  engines  and  apparatus  upon  which  the  progress  of  the  whole 
work  depends  must  always  be  in  perfect  condition,  and  this  is 
especially  true  of  all  parts  which  are  hard  to  get  at.  Careful  atten- 
tion to  repairs  and  proper  setting  up  of  machinery  tend  greatly  to 
prevent  disturbances  and  accidents  during  the  working  period. 

Not  only  should  the  boilers  be  tested  to  see  that  they  are  tight 
and  capable  of  standing  pressure,  but  the  evaporating-,  boiling-,  and 
heating-apparatus  should  be  carefully  examined  to  see  if  they  are 
in  good  shape  for  another  campaign.  Heating-coils  which  are  to  be 
heated  with  direct  steam  from  the  boilers  should  be  tested  with 
a  water-pressure  which  is  at  least  one  or  two  atmospheres  higher 
than  the  greatest  steam-pressure  to  which  they  are  likely  to  be  sub- 
jected. With  the  apparatus  which  is  heated  with  low-pressure 
steam  the  water-pressure  from  the  tanks  is  usually  sufficient  if  it 
has  about  one  atmosphere  overpressure  (15  Ibs.).  In  carrying  out 
these  tests  the  different  cocks  connected  with  the  different  forms 
of  apparatus  should  be  set  in  their  proper  position.  It  is  advisable 
to  test  not  only  the  heating-spaces  but  also  the  boiling-space  of 
evaporating-apparatus  with  water-pressure,  after  it  has  been  boiled 
out  with  acid. 

All  heating-tubes  and  steam-coils  must,  of  course,  be  freed  from 
any  scale  that  has  deposited  upon  them.  The  mineral  deposits 
must  also  be  carefully  removed  from  the  condensers,  defecating-, 


296  BEET-SUGAR  MANUFACTURE. 

and  carbonatation-pans,  and  all  of  the  piping  through  which  juice 
passes. 

All  of  the  valves  and  cocks  should  be  taken  apart  and  exam- 
ined, discs  and  seats  well  ground,  and  any  imperfect  washers  of 
rubber  or  vulcanized  fibre  renewed,  particularly  in  the  valves  of 
the  diff users,  carbonatation-apparatus,  filter-presses,  and  exhaust- 
steam  and  vapor  lines. 

In  localities  where  frost  can  penetrate  into  the  factory  after 
the  close  of  the  campaign,  the  steam  cylinders,  piping,  and  valves 
must  be  disconnected  and  left  open  so  that  they  will  always  be 
free  from  water;  otherwise  ice  may  form  in  the  pipes,  perhaps 
causing  them  to  burst. 

When  it  is  customary  to  keep  the  different  pipes  well  painted 
it  is  well  to  use  different  colors,  so  as  to  show  which  liquid  flows 
through  them. 

Before  beginning  work  with  the  beets,  all  of  the  machinery, 
the  different  apparatus  and  piping,  etc.,  should  be  tested,  at  first 
separately  and  then  a  test  is  made  with  water,  in  which  all  of 
the  operations  are  carried  out  that  the  juices  are  to  undergo.  If 
everything  is  then  found  to  be  in  satisfactory  working  condition 
it  is  reasonable  to  expect  that  there  will  be  little  trouble  at  the 
beginning  of  the  campaign. 


CHAPTER  XXVIII. 

THE  UTILIZATION  AND  DISPOSAL   OF  THE    WASTE-PRODUCTS 
AND  SWEET-WATERS. 

OF  the  different  waste-products  in  a  beet-sugar  factory  the  fol- 
lowing are  worthy  of  consideration:  the  press-cake  or  carbonata- 
tion-scums  from  the  filter-presses,  the  beet-earth  from  the  silos 
and  settling- tanks,  and  the  beet-tops. 

Filter-press  cake  (scum)  is  usually  considered  a  very  desirable 
fertilizer  for  the  soil.  Besides  calcium  carbonate  it  contains  phos- 
phoric acid,  nitrogen,  and  potash.  The  percentage  composition 
depends  not  only  upon  the  .amount  of  water  present,  but  also  upon 
the  amount  of  these  substances  which  were  present  in  the  beets,  and 
upon  the  amount  of  lime  used  in  the  defecation.  The  water-con- 
tent usually  varies  between  40  and  50  per  cent.  With  an  equal 
amount  of  water  present,  and  under  otherwise  similar  conditions, 
the  highest  percentage  of  phosphoric  acid  and  nitrogen  is  obtained 
when  the  least  lime  is  used  in  defecation;  for  when  1.75  per  cent, 
of  lime  is  used  the  same  amount  of  phosphoric  acid  and  nitrogen 
is  present  in  7  per  cent,  of  the  cake  as  will  be  present  in  12  per 
cent,  of  the  cake  when  3  per  cent,  of  lime  is  used.  It  is  evident, 
then,  that  the  chief  cause  for  the  varying  percentage  composition 
of  the  press-cake  is  due  to  different  amounts  of  lime  used  in 
defecating.  The  following  is  an  average  chemical  analysis  of  the 
dried  scums:  Phosphoric  acid,  1  to  2.5  per  cent.;  nitrogen,  0.2  to 
0.4  per  cent.;  potash,  0.05  to  0.3  per  cent.;  carbonate  of  lime, 
55  to  75  per  cent. ;  organic  matter,  10  to  15  per  cent. 

The  physical  nature  of  press-cake  has  an  important  influence 
upon  its  value.  As  it  is  obtained  in  the  factory  it  constitutes 
a  hard,  dirty,  greasy  mass  which  cannot  be  ground  up  easily, 

297 


298  BEET-SUGAR  MANUFACTURE. 

and  if  added  in  this  condition  it  lies  upon  the  ground  in 
larger  or  smaller  lumps,  which  naturally  exert  no  effect  upon  the 
soil.  If  it  is  kept  in  heaps  for  some  time,  or  if  it  is  mixed  with  earth 
and  allowed  to  dry,  it  becomes  brittle  and  is  then  an  excellent 
fertilizer  with  a  quick  action.  If  the  soil  is  deficient  in  lime  it  is 
well  to  mix  the  cake  in  a  mixing-apparatus  with  powdered  lime. 
In  this  way  a  finely  powdered  mass  is  obtained  which  is  easily 
distributed  over  the  soil  and  must  act  quickly  upon  it. 

In  some  factories  the  press-cake  is  mixed  with  water  into  a 
paste,  and  this  is  then  allowed  to  run  into  the  wash-water,  and 
becomes  well  mixed  in  the  settling-tanks  with  the  earth  from  the 
beets.  In  this  way  a  very  good  composite  earth  is  obtained  which 
is  often  highly  prized  by  farmers  in  the  vicinity  of  the  factor}-;  it 
would  not  be  economical  to  pay  freight  on  it. 

Cost  of  transportation  likewise  stands  in  the  way  of  the  practical 
utilization  of  the  soil  deposited  from  beets  in  the  settling-tanks. 
This  earth,  however,  makes  a  very  good  fertilizer,  and  it  is  usually 
easy  to  get  rid  of  it  without  incurring  expense.  Mud  scrapers, 
which  often  are  easily  constructed,  as  well  as  wheel  elevators, 
have  proved  very  useful  for  taking  up  the  semi-liquid  mud  deposit 
and  transferring  it  to  level  ground  for  drying.  By  such  an  ar- 
rangement any  deposit  space  is  done  away  with  and  the  mud  dries 
much  quicker  and  is  handled  easier. 

A  valuable  waste  material  are  beet-tails  which  drop  down 
with  the  water  and  dirt  through  gratings  and  small  openings  in 
carriers,  rakes  and  washers,  the  amounts  of  this  material  de- 
pending on  the  quality  of  the  beets,  and  the  way  they  are  un- 
loaded, transported  and  washed,  as  well  as  the  width  of  gratings 
and  openings.  The  quantity  usually  varies  from  1-2^  per  cent,  rf 
the  beets.  The  sugar  contained  depends  on  the  size  of  the  tail, 
the  thicker  ones  having  approximately  the  same  as  the  beet,  the 
finer  ones  containing  only  2-4  per  cent.  The  average  sugar 
content  can  be  taken  as  8-10  per  cent.,  the  dry  substances  as 
12-16  per  cent. 

The  water  from  hydraulic  carriers  and  washers  is  passed  over 
beet-tail  catchers  to  remove  the  tails.  These  are  built  like  chip 


WASTE-PRODUCTS    AND  SWEET-WATERS,  -JIM) 

catchers  and  have  long  slitted  sieves  which  are  kept  clean  by 
scrapers  or  brushes  or  are  apparatus  with  drum  sieves.  Naturally, 
all  the  larger  impurities  of  this  nature  in  the  water  are  likewise 
caught,  such  as  leaves,  weeds  and  stones. 

The  simplest  use  for  these  tails  is  directly  as  a  fodder.  They 
must  be  fed  promptly,  as  they  soon  sour  and  the  cattle  will  not 
oat  them.  Hence,  as  it  is  seldom  possible  to  feed  the  tails  at  once, 
they  are  more  conveniently  mixed  with  the  pulp  residues  for 
foddering  or  ensilage. 

These  tails  could  be  utilized  much  better  if  chopped  up  and 
put  into  either  the  diff users  or  driers.  Putting  them  in  the 
diffusers  is  most  profitable,  as  the  greater  part  of  their  sugar  will 
be  extracted  in  the  juice,  the  balance  going  to  the  pressed  chips. 

The  purity  of  the  juice  extracted  from  the  beet-tails  is  of 
course  less  than  from  the  normal  beet  juice,  rarely  reaching  80, 
but  usually  being  70-7"). 

Nevertheless,  good  massecuites  are  obtained  after  the  lime 
purification,  so  that  putting  the  beet -tails  into  the  diffusers  gives 
a  distinctly  greater  sugar  yield. 

These  beet  pieces  must  be  washed  and  freed  from  stones  before 
they  are  cut  up,  for  which  small  washers,  built  on  the  principle  of 
the  ordinary  beet  washers,  serve.  The  cutting  up  is  done  by 
special  machines,  usually  having  two  toothed  wheels  running  in 
opposite  directions,  slicing  machines  not  working  on  account  of 
fibre  and  leaves.  The  cuttings  are  mixed  with  the  fresh  chips  for 
diffusion,  pressing  and  drying. 

The  beet-tail  cuttings  are  somewhat  less  extracted  in  the 
diffusion  than  are  the  regular  chips,  but  at  least  70-80  per  cent, 
of  their  sugar  is  extracted  in  the  juice.  The  dried  product  repre- 
sents 12-16  per  cent,  of  the  fresh  beet-tails. 

Beet-tops  which  are  removed  mechanically  from  the  dirty 
waters  are  prized  as  fodder  and  paid  for  according  to  their  food- 
value.  Recently  they  have  been  cut  up  and  either  extracted 
with  the  chips  or  dried  directly. 

The  waste-waters  from  the  factory  are  always  a  source  of 
more  or  less  care  and  expense.  The  dirty  waters  leaving  the 


300  BEET-SUGAR    MANUFACTURE. 

factory  are  from  the  hydraulic  carriers,  the  beet-washers,  and  the 
waste-waters  from  diffusers  and  filter-presses.  If  the  press-cake 
is  mashed  with  water  and  pumped  to  settling  tanks,  there  is  this 
clarified  water  in  addition.  Only  in  exceptional  cases  would  pure 
water  be  mixed  with  these  waste-waters,  as  any  excess  of  pure 
water  is  utilized  for  hydraulic  carriers  or  recovered.  The  amount 
of  waste  water  for  each  100  Ibs.  of  beets  is  about  as  follows: 

From  the  carriers  and  washers 60  to  84  gallons 

From  the  diffusion  and  waste-waters.  13. 2  "  18       " 

From  the  chip  presses 3.6  "  6       " 

Other  wash-  and  waste-waters 0.6  "  1.2    " 

Total 77.4  to  109.2  " 

For  a  factory  working  up  about  1000  tons  of  beets  daily 
the  amount  of  water  used  is,  therefore,  from  1.6  to  2.2  million 
gallons. 

In  these  waste-waters  the  floating  particles  are  not  the  most 
injurious,  but  the  dissolved  constituents.  The  solid,  floating  part 
can  be  removed  at  once  by  the  beet-tail  and  pulp  strainers  and 
subsequent  settling  in  decanting  tanks  of  appropriate  size. 

It  is  very  advantageous  to  treat  the  waste  waters  in  separate 
lots,  taking  the  hydraulic-carrier  and  wash-waters,  which  are 
particularly  dirty,  as  one  and  the  waters  from  the  diffusion  as 
another  portion.  The  latter  contain  by  far  the  most  organic 
matter,  about  0.15-0.30  per  cent,  of  sugar  or  1500-3000  grams 
in  a  cubic  meter  (12.5-25  Ibs.  per  1000  gals.),  and  practically  the 
same  amount  of  non-sugar  of  which  the  major  part  is  organic. 
It  should  be  remembered  that  this  dirty  sugar  and  organic  matter 
comes  out  of  the  beets,  the  water  holding  at  least  20-50  grams  of 
sugar  per  cubic  meter  (.17-.42  Ibs.  per  1000  gals.),  rising  with 
frozen  beets  to  500  grams  (4.2  Ibs.  per  1000  gals.). 

Only  a  few  factories  are  so  fortunately  situated  as  to  have  an 
abundant  supply  of  pure,  fresh  water  for  all  departments,  and  at 
the  same  time  be  able  to  discharge  all  the  mechanically  cla-rified 


WASTE-PRODUCTS  AND  SWEET-WATERS.  301 

waste-waters  into  a  large  stream.  In  all  other  factories  the  solu- 
tion of  the  water  problem  depends  on  whether  the  waste-waters 
must  be  used  over  again,  owing  to  the  plant  being  short  of  water' 
or  because  of  the  difficulty  of  their  disposal.  In  either  case  the 
endeavor  is  to  draw  out  as  little  of  these  waters  as  possible.  For 
the  purification  of  the  unavoidable  waste-waters,  the  aim  is  to 
convert,  by  fermentation  or  oxidation,  the  complicated  organic 
substances  whir-h  the  water  contains  into  their  simplest  or,  so  to 
speak,  inorganic  constituents;  as,  for  instance,  sugar  into  water 
and  carbonic  dioxide,  nitrogenous  substances  into  ammonia  and 
nitrates. 

The  amount  of  waste-waters  can  be  reduced  the  most  by 
separating  the  diffusion  waste-waters  and  working  them  back, 
either  in  the  diffusers,  the  presses  or  in  the  scalding  process. 

Another  way  of  recovery  of  the  waste-waters  is  to  allow  the 
diffusion  waters  to  ferment,  without  lime,  in  separate  basins, 
either  by  themselves  or  after  mixing  with  the  clarified  foul  waters. 
The  resulting  clarified  acid  waters  are  used  for  general  diffusion 
purposes  and  pressure  water.  This  makes  no  trouble  in  the 
diffusion  if  the  temperature  of  the  last  cell  is  brought  up  to  70°- 
80°  C.  (160°-175°  F.)  as  quickly  as  possible,  the  resulting  juice 
and  sugar  being  of  normal  quality.  Nevertheless,  this  method 
of  waste-water  utilization  should  only  be  looked  to  as  a  last  resort 
as  such  waters  contain  notable  amounts  of  injurious  -non-sugars 
which  must  lower  the  purity  of  liquors  and  massecuites.  More- 
over, pumps,  piping  and  filter-press  screens  are  injured  by  the 
strongly  acid  water,  and  often  the  odor  of  sulphuretted  hydrogen 
is  by  no  means  a  pleasant  accompaniment. 

Nowadays  almost  everyone  has  given  up  the  use  of  chemical 
agents  for  precipitating  the  soluble  impurities  in  unfermented 
waste-waters  and  for  the  hastening  the  settling.  On  the  other 
hand,  calcium  carbonate,  cheapest  in  the  form  of  press  scums,  is 
known  to  be  of  much  advantage  both  in  fermented  and  un- 
fermented waters,  as  it  neutralizes  the  acid  and  the  fermenta- 
tion proceeds  much  more  energetically  in  neutral  or  weakly  acid 
solutions. 


302  BEET-SUGAR  MANUFACTURE. 

Caustic  lime  purifies  fermented  waters  to  a  considerable  extent, 
as  it  precipitates  organic  matter.  Hence,  addition  of  milk  of 
lime  is  strongly  recommended.  This  fermentation  is  carried  out 
in  wooden  tanks  as  the  ingenious  apparatus  used  for  purifying 
city  sewage  is  not  practicable  for  this  purpose  owing  to  the  large 
amounts  of  unfermentable  and  putrefactive  matter. 

The  fermented  water  which  in  certain  instances  is  again  puri- 
fied with  lime  is  usually  put  on  a  filter-bed,  whence  it  comes  pure 
as  far  as  is  possible  according  to  the  present  state  of  our  knowl- 
edge. The  success  of  this  purification  depends  especially  on  the 
care  exercised  in  over.  e?:n^  the  different  stages  of  process  and 
upon  having  the  rotting  tanks  and  filter-beds  of  sufficient  size. 

The  problem  of  complete  purification  of  the  waste-waters  from 
a  sugar-factory  is,  therefore,  an  unsolved  one,  and  is  probably  not 
capable  of  solution.  It  cannot  be  expected  that  the  water  be 
completely  purified,  and  local  circumstance  will  decide  to  what 
extent  this  purification  is  necessary  and  can  be  carried  out. 
Where  the  water  can  be  let  into  a  large  stream  simple  clarifi- 
cation in  the  settling-tanks,  together  with  the  self-purification 
of  the  running  water,  is  sufficient  to  make  impurities  uninjurious 
in  a  short  time,  and  if  small  amounts  of  slime  do  run  off  with 
the  water  they  do  no  harm.  Moreover,  the  dissolved  impurities 
through  the  self -purification  of  the  stream  soon  become  harmless. 
The  smaller  the  stream  the  less  the  dilution  of  the  waste-water, 
and  hence  the  more  thorough  must  be  the  purification  to  insure 
harmlessness  and  the  greater  the  necessity  of  cutting  down  the 
waste-waters  and  utilizing  them  in  process. 

The  waste-waters  from  a  sugar-factory  are  not  injurious  to  the 
health  of  man  or  beast,  but  when  there  are  only  small  streams  of 
running  water  for  their  disposal  they  may  be  capable  of  producing 
very  disagreeable  phenomena.  They  are  not  of  themselves  directly 
injurious  to  the  fish  in  the  streams,  but  this  cannot  be  said  of  molds 
which  are  formed  from  them.  In  the  course  of  time  these  molds 
may  decay  and  in  the  process  generate  so  much  hydrogen-sulphide 
gas  that  all  of  the  fish  may  be  killed. 

To  determine  to  what  extent  the  purification  of  waste-waters 


WASTE-PRODUCTS  AND  SWEET-WATERS.  303 

should  be  carried  out  it  is  necessary  to  know  the  nature  of  the 
organisms  developed  in  the  stream  into  which  they  go.  There  are 
three  kinds  of  micro-organisms  which  need  chiefly  to  be  considered: 
Icptomitus,  sphcerotilus,  and  beggiatoa.  Leptomitus  is  found  in  rela- 
tively pure  waters,  so  that  its  formation  indicates  that  the  water 
has  been  sufficiently  purified.  Sphcerotiliis  develops  in  impure 
water,  while  beggiatoa  occurs  in  ill-smelling  water  containing  putrid 
matter;  these  two  latter,  therefore,  indicate  that  the  water  has  not 
been  sufficiently  purified. 


CHAPTER   XXIX. 


ANALYSIS   OF  BEETS,  SIRUPS,  AND   SUGAR    PRODUCTS. 

THE  AVERAGE  COMPOSITION  OF  JUICES,  SIRUPS,  MASSECUITES,  AND  SUGARS 
OP  A  FACTORY  FOR  THE  CAMPAIGN,  1898-99. 

(a)   JUICES  AND  SIRUPS. 


g 

Thick  juice. 

Purged  sirup. 

0) 

2 

g 

•+a  8 

I 

'3 

| 

o.2 

A  «- 
.8 

| 

1 

3 

J 

•i. 

1 

1 

1 

I 

1 

-2  *? 

3 

i 

"eS  . 

PH 

PM 

cd 

« 

5 

02 
i-t 

g 

C 
£3 

1 

«   . 

|o 

Brix 

14.4 



12.2 



53.3 

77.4 

76.4 

82.8 

Polarization 

14.66 

12.2 



10.9 



48.0 

56.9 

49.1 

47.8 

Apparent  quotient 
Alk.  phenolphtha- 

84.7 



89.3 

— 

90.1 

73.6 

64.3 

57.7 

lei'n  

— 

— 

0.091 

0.049 

0.142 

0.049 

0.11 

0.11 

0.08 

Alk.  rosolic  acid  .  . 





0.11 

0.067 

— 

0.075 

— 

— 

— 

Lime  (by  volume) 

— 

— 

— 

0.043 

— 

0.16 

— 

— 

1.6 

Invert  sugar  

0.17 

0.18 

— 

— 

— 

— 

— 

— 

— 

Acid     (ccm.    nor- 

mal   acid)   phe- 

nolphthale'in.  .  . 

.  — 

2.1 

— 

— 

— 

— 

— 

— 

— 

(6)    MASSECUITES,   SUGAR,   AND  MOLASSES. 


Thick 
juice. 

Massecuites. 

Molasses. 

Raw  sugar. 

Boiled 
with 
sirup. 

II. 

III. 

I. 

II. 

III. 

Polarization  
Water  
Ash  (SO3)  
Organic  non-sugar  .  . 
True  purity  
Alkal.  phenolphthal. 
Lime       

47.9 
47.7 
1.72 
2.67 
91.6 
0.039 
0.12 

83.5 
7.55 
3.48 
5.47 
90.3 
0.064 
0.27 

67.1 
10.42 
8.52 
13.96 
74.9 
0.12 
0.62 

58.7 
11.5 

66.4 
0.14 
0.76 

47.8 
21.83 
11.78 
18.59 
61.1 
0.08 
1.6 

96.1 
1.50 
0.93 
1.47 

0.011 

92.1 
2.56 
2.07 
3.27 

0.035 

90.8 
2.70 

2.81 
3.69 

0.030 

For  100  polarization  : 
Ash  
Organic  non-sugar 
Lime          

3.6 
5.6 
0.25 
0.08 

4.1 
6.6 
0.32 
0.08 

12.7 

20.8 
0.93 
0.17 

1.29 
0.24 

24.6 
38.9 
3.3 
0.16 

— 

— 

— 

Alkalinity  

Organic  non-sugar: 
Ash 

1.55 

1.57 

1.64 

— 

1.58 

1.58 

1.60 

1.32 

304 


ANALYSIS^  BEETS,   SIRUPS,  AND  SUGAR  PRODUCTS.  305 


CAMPAIGN  OF  1902-03. 

(a)    JUICES    AND   SIRUPS. 


§ 

o 

Thick  juice. 

3 

d 
.i 

r 

'= 

•8 

il 

= 

1 

£ 

i 

- 

B 

. 

J 

I 

9 

3 

3 

"S 

1 

•a 

| 

r 

ta 

5 

-H- 

H 

p 

"5 

O) 

o 

Brix  



14.0 



12.6 



59.6 

81.0 

83.8 

Polarization  

14.91 

12.1 



11.5 

— 

55.0 

60/6 

49.8 

Apparent  quotient  
Alkal.:  Phenolphthal..  . 
Rosolic  acid  .... 

= 

85.5 

0.093 
0.11 

91.5 
0.041 
0.051 


0.133 

92.3 
0.045 
0.064 

74.9 
0.142 

59.4  . 
0.18 
0.26 

Lame  (volume  per  cent)  . 

— 

— 

— 

0.035 

— 

0.101 

— 

0.60 

(6)    MASSECUITES,   SUGAR,   AND   MOLASSES. 


Thick 
jaice. 

Massecuites. 

j 

Raw  sugar. 

Boiled 
with 
sirup. 

II 

I. 

II. 

Polari  zati  on 

54.9 
41.0 
1.63 
2.47 
93.1 
0.034 
0.080 

84.7 
6.93 
3.24 
5.13 
91.0 
0.062 
0.16 

70.4 
7.32 
8.56 
13.72 
75.9 
0.137 
0.40 

49.7 
19.33 
11.92 
19.05 
61.6 
0.14 
0.60 

95.15 
1.40 
0.88 
1.56 
97.5 
0.013 

94.0 
1.85 
1.60 
2.55 
95.8 
0.020 

Water 

Ash  (SO3)                                

Organic  non-sugar  
True  purity  
Alkal.  (phenolphthalein)  

Lime 

For  100  polarization: 
Ash 

3.0 
4.5 
0.14 
0.06 

3.8 
6.1 
0.19 
0.11 

12.2 

19.6 
0.57 
0.19 

24.0 
38.3 
1.2 
0.28 

— 

— 

Organic  non-sugar  
Lime 

Alkalinity                

Organic  non-sugar: 
Ash 

1.52 

1.60 

1.61 

1.60 

1.77 

1.62 

306 


BEET-SUGAR  MANUFACTURE. 


SUMMARY 

OP  THB  ALKALINITY  (PHENOLPHTHALE'IN)  OP  JUICES,  SIRUPS,  MASSECUITES, 
AND  SUGAR  OF  A  FACTORY  FOR  DIFFERENT  YEARS. 


Method  of  Boiling. 

Sirups  blank  boiled. 

Boiled  to  grain. 

1896-97. 

1897-98. 

1898-99. 

1900-01. 

1901-02. 

Pol. 

Alk. 

Pol. 

Alk. 

Pol. 

Alk. 

Pol. 

Alk. 

Pol. 

Alk. 

Juice,    I  saturation. 
Juice,  II  saturation. 
Thin  juice.  
Unsat.  thick  juice  .  . 
Sat.  thick  juice  

10.2 
53.5 

82.6 
95.2 
54.2 
63.5 
92.2 
55.5 
92.1 
48.3 

0.082 
0.021 
0.021 

0.034 

0.038 
0.006 
0.100 
0.077 
0.006 
0.092 
0.007 
0.080 

10.7 
51.5 

83.3 

96.0 
57.9 
66.3 
93.5 
50.4 
92.0 
48.2 

0.072 
0.043 
0.042 
0.100 
0.035 

0.063 
0.011 
0.109 
0.108 
0.016 
0.132 
0.024 
0.120 

10.9 
48.0 

83.5 
96.1 
56.5 
67.1 
92.1 
58.7 
90.8 
47.8 

0.087 
0.048 
0.047 
0.110 
0.039 

0.064 
0.011 
0.110 
0.120 
0.015 
0.140 
0.010 
0.080 

10.5 

50.6 

83.5 
96.4 
59.0 
68.5 
93.2 

49.5 

0.084 
0.043 
0.041 
0.095 
0.030 

0.044 
0.011 
0.046 
0.092 
0.013 

0.075 

10.1 

52.8 

82.2 
96.4 
58.9 
67.0 
93.7 

50.5 

0.089 
0.039 
0.034 
0.093 
0.033 

0.043 
0.008 
0.104 
0.082 
0.012 

0.103 

Massecuite      cooked 
with  sirup 

I.  Raw  sugar  
I.  Purgings          .  . 

II.  Massecuite  
II.  Raw  sugar  
III.  Massecuite  
III.  Raw  sugar  
Molasses 

ANALYSES  OF  BEETS  FROM  DIFFERENT  PROVINCES. 
September  22,  1898. 

(Herzfeld,  Vereinszeitschrift  1898,  S.  828.) 


Province. 

Average 
weight 
in  grams. 

Proportion 
of  beet 
to  leaves. 

Composition. 

One 
beet. 

Of 
leaves. 

Sugar. 

Total 
ash. 

Sole 
ash. 

Nitro- 
gen. 

Mark. 

Silesia  
Pommerania  
Saxony  1    

416 
340 
458 
320 
412 
352 

516 
217 
363 
300 
321 
428 

1.24 
0.64 
0.71 
0.94 
0.78 
1.22 

12.9 
16.7 
16.6 
14.9 
15.2 
13.7 

0.95 
0.72 
1.01 
0.82 
1.03 
1.12 

0.83 
0.45 
6.82 
0.60 
0.48 
0.59 

0.24 
0.20 
0.21 
0.16 
0.17 
0.18 

4.95 
4.37 
5.15 
5.23 

4.84 
4.71 

Saxony  2  

Hanover 

Rhine       

ANALYSIS  OF  BEETS,  SIRUPS,  AND  SUGAR   PRODUCTS.    307 


AKALYSIS  OF  DIFFUSION  JUICES,  MASSECUITES,  AND  MOLASSES  FROM 
BOHEMIAN  FACTORIES. 

(Andrlik,  Bohm.  Zeitschrift  1900,8.203-264;  1901,8.247;  und  1907,  S.  441.) 
(Campaign  1898-99.) 


Diffusion  juice. 

Massecuite. 

Factory. 

a 

b 

c     \     d 

€ 

a 

6 

c 

d 

e 

Polarization.  . 

_ 







90.7 

90.5 

87.6 

87.15 

85.75 

Water 











3.06 

4.72 

4.55 

4.88 

6  02 

Ash  (carb'n'd) 

— 

— 

— 

— 



2.14 

2.16 

2.49 

2.66 

2.32 

Org.  non-sugar 

— 

—  r 

— 

— 



4.10 

3.62 

5.36 

5.32 

5.91 

§uotient  

— 

— 

— 

— 



93.5 

93.9 

91.8 

91.6 

91.2 

rg.non-sugar: 

Ash  

— 

— 

— 

— 



1.9 

1.7 

2.1 

2.0 

2.5 

Alk.  phenol. 

— 

— 

— 

— 



0.017 

0.004 

acid 

0.028 

acid 

On   100  parts  of  dry  substance. 

Total  ash  

2.77 

3.09 

3.81 

3.79 

3.23 

2.21 

2.24 

2.61 

2.80 

2.47 

Potash  

1.34 

1.36 

1.72 

1.55 

1.40 

1.25 

1.19 

1.37 

1.59 

1.41 

Soda  

0.12 

0.09 

0.16 

0.19 

0.11 

0.15 

0.20 

0.27 

0.19 

0.13 

Lime  

0.06 

0.04 

0.03 

0.06 

0.12 

0.01 

0.02 

0.02 

0.03 

0.04 

Phos.  acid.  . 

0.37 

0.49 

0.64 

0.49 

0.35 

0.005 

0.011 

0.003 

0.014 

0.009 

Sulph.  acid  . 

0.22 

0.17 

0.18 

0.24 

0.24 

0.13 

0.17 

0.10 

0.14 

0.17 

Chlorine  

0.05 

0.08 

0.07 

0.08 

0.09 

0.10 

0.06 

0.07 

0.07 

0.07 

Total  nitrogen 

0.87 

0.90 

0.75 

1.31 

0.80 

0.37 

0.41 

0.56 

0.45 

0.57 

Albuminoid 

nitrogen  .  . 

0.30 

0.28 

0.26 

0.29 

0.32 

0.03 

0.03 

0.05 

0.(M 

0.04 

Ammonia  ni- 

trogen. .  .  . 

0.11 

0.15 

0.09 

0.11 

0.10 

0.06 

0.03 

0.05 

0.03 

0.02 

Amino    acid 

nitrogen  .  . 

0.44 

0.21 

0.32 

0.38 

0.33 

0.24 

0.26 

0.40 

0.27 

0.44 

Oxalic  acid  .  .  . 

0.40 

0.80 

0.91 

0.66 

0.66 

— 

— 

— 

— 

— 

308 


BEET-SUGAR   MANUFACTURE. 


COMPARATIVE  SUMMARY 

OF  THE  COMPOSITION  OF  DIFFERENT  JUICES  OF  1899-1900   (NORMAL 
WEATHER)  AND  THOSE  OF  1904-5  (VERY  DRY  YEAR)  PER  100  PARTS  SUGAR. 


Per  100  parts  sugar. 

1899-1900. 

1904-05. 

Potash 

1.58 
0.22 
0.19 
0.08 
0.47 
0.71 
0.72 
0.24 
0.10 
0.10 
0.28 
0.53 

1.11 

0.17 
0.21 
0.06 
0.27 
0.49 
0.93 
0.22 
0.17 
0.24 
0.29 
0.36 

Soda 

Sulphuric  acid  

Chlorine     

Phosphoric  acid 

Oxalic  acid 

Total  nitrogen                                               .  . 

Albuminoid  nitrogen                   .  .        

Ammonia  and  amino  nitrogen 

Betain  nitrogen          

Other  nitrogen          

Acidity 

MOLASSES. 


Factory. 

1 

2 

3 

4 

5 

6 

7 

8 

Polarization  
Saccharose  (Herzfeld)  

47.2 
48.8 
21.64 
8.68 
20.88 
62.3 
2.4 

48.0 
49.8 
20.35 
9.14 
20.71 
62.5 
2.3 

47.4 
47.9 
20.66 

8.71 
22.77 
60.3 
2.6 

46.6 
47.9 
18.14 
10.10 
23.86 
58.5 
2.4 

49.0 
49.2 
16.87 
10.95 
22.98 
59.2 
2.1 

47.4 

47.7 
19.91 
10.49 
21.90 
59.6 
2.1 

47.2 
47.5 
22.49 
9.54 
20.43 
61.3 
2.2 

51.1 
51.5 

18.80 
9.11 
20.63 
63.4 
2.3 

Water 

Ash  (carbonated)  .  .  .  
Organic  non-sugar 

Quotient            

Organic  non-sugar:  Ash.  .  . 
Total  ash  

In  100  parts  dry  substance. 

11.08 
6.29 
0.84 
0.14 
0.04 
0.01 
0.18 
0.38 
2.22 
0.22 
0.07 
1.24 
0.06 

11.48 
6.52 
0.87 
0.22 
0.04 
0.03 
0.21 
0.42 
2.47 
0.18 
0.06 
1.36 
0.07 

10.98 
6.26 
0.81 
0.19 
0.04 
0.04 
0.17 
0.39 
2.37 
0.26 
0.04 
1.15 
0.06 

12.37 
6.66 
1.00 
0.14 
0.21 
0.04 
0.56 
0.48 
2.62 
0.19 
0.09 
1.47 
0.02 

13.18 
7.07 
1.09 
0.21 
0.03 
0.08 
0.37 
0.48 
2.50 
0.14 
0.07 
1.59 
0.09 

13.10 
6.60 
1.41 
0.19 
0.04 
0.07 
0.31 
0.50 
2.40 
0.13 
0.08 
1.63 
0.02 

12.31 
6.71 
0.72 
0.59 
0.05 
0.04 
0.15 
0.43 
2.41 
0.29 
0.07 
1.22 
0.04 

11.21 
6.20 
1.09 
0.09 
0.05 
0.10 
0.16 
0.37 
2.24 
0.17 
0.05 
1.46 
0.02 

Potash  

Soda 

Lime 

Magnesia             .... 

Phosphoric  acid 

Sulphuric  acid  
Chlorine  

Total  nitrogen  

Albuminoid  nitrogen  .... 
Ammonia  nitrogen  
Amino  acid  nitrogen  .... 
Nitrate  nitrogen  

APPENDIX  I. 

309 


FORMULAE   AND  TABLES. 

THE  following  tables,  formulae,  and  general  data  are  those 
which  interest  the  technical  sugar  men  chiefly.  It  seems  wise  to 
add  them  to  the  book,  partly  because  they  are  not  generally 
given  in  the  other  works  and  calendars  on  sugar-making,  or  at 
best  in  an  incomplete  or  incomprehensive  form.  Only  those 
tables  and  formulae  are  given  which  it  is  believed  may  prove  of 
benefit  particularly  in  the  factoiy  control. 

FORMULA. 

1.  Formula  for  calculating  the  weight  of  water  (W)  which  must 
be  evaporated  from  G  pounds  of  thin  juice  at  b°  Brix  to  give  a  thick 
juice  of  B°  Brix: 


2.  Formula  for.  calculating  the  amount  (F)  of  thick  juice  (masse- 
cuite)   of  B°  Brix  which  will   be  obtained  from  G  pounds  of  thi?i 
juice  ai  b°  Brix: 

'-4 

Remark:  In  the  above  formulae  for  accurate  computation  the 
true  weight  of  the  dry  substance  should  be  taken  rather  than  the 
apparent  weight. 

3.  Formulae  for  calculating  yield : 

Let  Fty  Zt,  St  =the  dry  substance  contained  respectively  in 

the  massecuite,  the  sugar,  and  the  sirup; 
FP,  Zp,  Sp=  polarization  of  the  massecuite,  the  sugar,  and 

the  sirup; 
Fq,  Zg,  Sq=the  quotient  (true)   of   the   massecuite,   the 

sugar,  and  the  sirup; 
x= yield  in  per  cent, 
(a)  Hulla-Suchomel's  formula: 


x  =100 


Ft(Fq-Sq) 
Zt(Zq-Sq)' 

310 


APPENDIX   I.  311 

(6)  Schneider's  formula: 

x 
(c)  Neumann's  formula: 


Remark.  —  Formula  (a)  is  generally  applicable,  even  when  the 
centrifugated  sirup  has  been  diluted  in  any  way;  formulae  (6)  and 
(c)  can  be  used  only  when  there  has  been  no  dilution  of  the  juice 
during  centrifugation. 

4.  Saturation  formula  for  sirups  : 

A  sirup  saturated  at  the  temperature  t,  of  true  purity  q,  has 
the  following  composition  (amount  of  water  W,  amount  of  sugar 
present  Z)  if  the  saturation  ratio  between  a  pure-sugar  solution 
at  the  temperature  t  =  Lt  and  the  coefficient  of  saturation  is  c: 


Lt-c  +  0.01g' 


If  the  composition  of  a  sirup  supersaturated  in  a  definite  way 
is  to  be  obtained,  then  the  coefficient  c  in  the  above  formula  should 
be  multiplied  by  the  corresponding  supersaturation-coefficient  c\9 
and  the  formula  is  then 


W 


5.  Formulae  for  evaporation  and  heating: 
(a)  Total  heat  of  the  saturated  steam  is 

/  =  606.5  +  0.305*. 

(6)  The  heat  of  evaporation  of  the  saturated  steam  is 
r  =  606.6  -0.695*, 

where  t  is  the  temperature  of  the  steam. 

(c)  The  amount  of  steam  (*S)  required  for  the  evaporation  of  one 
kilogram  (2.2  Ibs.)  of  water,  when  the  temperature  of  the  boiling 


312  APPENDIX^  I. 

juice  is  t9,  that  of  the  steam  is  k?  and  that  of  the  condensed  water 

606.5-0.695^ 
~  606.5  +  0. 305k  -tc[ 

or  if  k  is  made  equal  to  tc,  which  is  approximately  true,  then 

„    606.5-0.695^ 
"606.5 -0.695k' 

(d)  Calculation  of  the  amount  of  steam  (S)  required  for  heating 
one  kilogram  (2.2  Ibs.)  of  juice  in  the  preheaters  when  the  tempera- 
ture of  the  steam  is  k>  of  the  condensed  water  tc,  of  the  juice  on 
entering  t±  and  on  leaving  t2: 


606.5  + 0.305  (k-y 

(e)  The  amount  of  steam  (S)  for  heating  one  kilogram  of  juice 
by  direct  steam,  using  the  same  notation  as  under  (d): 


606. 

6.  Formula  for  the  condensation  of  steam: 

The  amount  of  water  (W)  required  to  condense  one  kilogram 
(2.2  Ibs.)  of  steam  when  its  temperature  is  ta,  that  of  the  injected 
water  is  £t-,  and  of  the  condenser-water  is  trt  is 


^606-5  +  Q.  305fa-.fr) 
tf-k 

7.  Formula  for  the  heat  transmission  through  a  metal  wall. 


H  is  the  total  quantity  of  heat,  A  the  area  of  heating  surface, 
ta  —  tb  the  temperature  fall,  D  the  thickness  of  the  wall  in 
millimeters,  and  C  the  conductivity  coefficient  for  the  material 


APPENDIX   I.  313 

composing  the  wall  (C  for  brass  being  1700,  for  iron  1400,  and 
for  water  14). 

In  calculations  based  on  this  formula,  the  thickness  of  the 
heat  wall  is  to  be  increased  to  allow  for  the  thickness  of  moving 
film  of  water  or  liquor,  an  undetermined  value  which  can  only 
be  approximated,  being  expressed  in  millimeters  of  metal  of 
the  same  conductivity. 

8.  Formula  for  the  fire-room. 

(a)  The  excess  of  air 

CO?  =0=  theoretical  air  necessary  (18.9  for  coal) 
CC>2  found  in  flue  gases 

T—  t 

(b)  The  heat  lost  in  the  flue  gases  =  ——— -k,  where  k  =0.66, 

\j\j2  lound 

T=  temperature  of  flue  gases,  and  J=the  temperature  of  the 
air. 


314 


APPENDIX  I. 


TABLES. 

1.  SOLUBILITY  OF  LIME  IN  WATER. 
(Herzfeld,  Deutsche  Vereinszeitschrift,  1897,  p.  819.) 


At  the  tem- 
perature of 

Parts  of  water 
for  one  part 
CaO. 

At  the  tem- 
perature of 

Parts  of  water 
for  one  part 
CaO. 

15°  C. 

776 

50°  C. 

1044 

20°  C. 

813 

55°  C. 

1108 

25°  C. 

848 

60°  C. 

1158 

30°  C. 

885 

65°  C. 

1244 

35°  C. 

924 

70°  C. 

1330 

40°  C. 

962 

75°  C. 

1410 

45°  C. 

1004 

80°  C. 

1482 

2.  SOLUBILITY  OF  LIME  IN  SUGAR  SOLUTIONS. 

According  to  Lamy,  there  will  dissolve  in  100  grams  of  ten  per  cent  sugar 
solution 

At     0° 25.0  grams  CaO 

"    15° 21.5      "        " 

"    30° 12.0      "        " 

"50° 5.3      " 

(t      7f)°  O    Q         "  « 

"100° 1.55     "  "  ; 

Remark. — The  solubility  of  lime  in  sugar  solution  depends  not  alone 
upon  the  temperature  and  the  amount  of  sugar  in  solution,  but  also  upon 
the  nature  of  the  lime  added,  as  well  as  the  duration  of  the  action. 

3.  TABLE  SHOWING  THE  AMOUNT  OF  CAUSTIC  LIME  CONTAINED  IN  MILK  OF 
LIME  AT  15°  C.  (BLATTNER). 


Deg. 
Brix. 

Degree 
Baumd. 

Weight 
of  one 
litre 
milk  of 
lime. 

CaO 
per 
litre. 

Per 
cent 
CaO. 

Deg. 
Brix. 

Degree 
Baumd. 

Weight 
of  one 
litre 
milk  of 
lime. 

CaO 

per 
litre. 

Per 
cent 
CaO. 

grams. 

grams. 

grams. 

grams. 

1.8 

1 

1007 

7.5 

0.745 

29 

16 

1125 

159 

14.13 

3.6 

2 

1014 

16.5 

1.64 

30.8 

17 

1134 

170 

15 

5.4 

3 

1022 

26 

2.54 

32.7 

18 

1142 

181 

15.85 

7.2 

4 

1029 

36 

3.5 

34.6 

19 

1152 

193 

16.75 

9 

5 

1037 

46 

4.43 

36.4 

20 

1162 

206 

17.72 

10.8 

6 

1045 

56 

5.36 

38.3 

21 

1171 

218 

18.61 

12.6 

7 

1052 

65 

6.18 

40.1 

22 

1180 

229 

19.4 

14.4 

8 

1060 

75 

7.08 

42 

23 

1190 

242 

20.34 

16.2 

9 

1067 

84 

7.87 

43.9 

24 

1200 

255 

21  .  25 

18 

10 

1075 

94 

8.74 

45.8 

25 

1210 

268 

22.15 

19.8 

11 

1083 

104 

9.6 

47.7 

26 

1220 

281 

23.03 

21.7 

12 

1091 

115 

10.54 

49.6 

27 

1231 

295 

23  .  96 

23.5 

13 

1100 

126 

11.45 

51  .  5 

28 

1241 

309 

24.9 

25.3 

14 

1108 

137 

12.35 

53.5 

29 

1252 

324 

25.87 

27.2 

15 

1116 

148 

13.26 

55.4 

30 

1263 

339 

26.84 

APPENDIX  I. 


315 


4.  TABLE  SHOWING  THE  SOLUBILITY-  OF  SUGAR  IN  WATER  AT  DIFFERENT 

TEMPERATURES. 

(Recalculated  from  Herzfeld,  Deutsche  Vereinszeitschrift,  1892,  p.  181.) 
One  part  of  water  will  dissolve — 


Tempera- 
ture. 
C.° 

Parts  of 
sugar. 

Tempera- 
ture, 
C° 

Parts  of 
sugar. 

Tempera- 
ture, 
C.° 

Parts  of 
sugar. 

Tempera- 
ture. 
C.° 

Parts  of 
sugar. 

0 

.79 

1 

.80 

26 

2.12 

51 

2.62 

76 

3.44 

2 

.81 

27 

2.14 

52 

2.65 

77 

3.48 

3 

.82 

28 

2.16 

53 

2.67 

78 

3.52 

4 

.83 

29 

2.17 

54 

2.70 

79 

3.57 

5 

.84 

30 

2.19 

55 

2.73 

80 

3.62 

6 

.86 

31 

2.21 

56 

2.75 

81 

3.66 

7 

.87 

32 

2.23 

57 

2.78 

82 

3.71 

8 

.88 

33 

2.25 

58 

2.81 

83 

3.76 

9 

.89 

34 

2  .  27 

59 

2.84 

84 

3.81 

10 

.90 

35 

2.29 

60 

2.87 

85 

3.86 

11 

.91 

36 

2.30 

61 

2.90 

86 

3.92 

12 

.92 

37 

2  .  32 

62 

2.93 

87 

3.98 

13 

.94 

38 

2.34 

63 

2.96 

88 

4.03 

14 

.96 

39 

2.36 

64 

2.99 

89 

4.09 

15 

.97 

40 

2.38 

65 

3.03 

90 

4.15 

16 

.98 

41 

2.40 

66 

3.06 

91 

4.21 

17 

.99 

42 

2.42 

67 

3.09 

92 

4.28 

18 

2.01 

43 

2.44 

68 

3.13 

93 

4.35 

19 

2.02 

44 

2.46 

69 

3.16 

94 

4.42 

20 

2.04 

45 

2.48 

70 

3.20 

95 

4.48 

21 

2.05 

46 

2.51 

71 

3.24 

96 

4.55 

22 

2.07 

47 

2.53 

72 

3.28 

97 

4.63 

23 

2.08 

48 

2.55 

73 

3.31 

98 

4.71 

24 

2.09 

49 

2.58 

74 

3.35 

99 

4.79 

25 

2.11 

50 

2.60 

75 

3.40 

100 

4.87 

316 


APPENDIX  I. 


5.  TABLE  OF  TEMPERATURES  CORRESPONDING  TO  THE  TENSIONS  OF  SATURATED 

STEAM. 

(Claassen,  Deutsche  Vereinszeitschrift,  1893.  p.  268.) 

I.     FOR  EVAPORATION. 
(a)  From  0  to  75  cm.  vacuum. 


Absolute 
pressure 
in  cm. 

Vacuum. 

Temperature. 

Absolute 
pressure 
in  cm, 

Vacuum. 

Temperature. 

cm. 

inches. 

C.° 

F.° 

cm. 

inches. 

C.° 

F° 

1 

75 

29.5 

11.3 

52.3 

23.5 

52.5 

20.7 

70.2 

158 

2 

74 

29.1 

22.4 

72.3 

24 

52 

20.5 

70.7 

159 

3 

73 

28.7 

29.1 

84.4 

24.5 

51.5 

20.3 

71.2 

160 

4 

72 

28.3 

34.2 

93.6 

25 

51 

20.1 

71.6 

161 

5 

71 

27.9 

38.3 

101 

25.5 

50.5 

19.9 

72.1 

162 

6 

70 

27.6 

41.7 

107 

26 

50 

19.7 

72.5 

162 

6.5 

69.5 

27.4 

43.2 

110 

26.5 

49.5 

19.5 

73.0 

163 

7 

69 

27.2 

44.6 

112 

27 

49 

19.3 

73.4 

164 

7.5 

68.5 

27.0 

46.0 

115 

27.5 

48.5 

19.1 

73.9 

165 

8 

68 

26.8 

47.2 

117 

28 

48 

18.9 

74.3 

166 

8.5 

67.5 

26.6 

48.4 

119 

28.5 

47.5 

18.7 

74.7 

166 

9 

67 

26.4 

49.6 

121 

29 

47 

18.5 

75.1 

167 

9.5 

66.5 

26.2 

50.7 

123 

29.5 

46.5 

18.3 

75.5 

168 

10 

66 

26.0 

51.7 

125 

30 

46 

18.1 

75.9 

169 

10.5 

65.5 

25.8 

52.7 

127 

30.5 

45.5 

17.9 

76.3 

169 

11 

65 

25.6 

53.6 

128 

31 

45 

17.7 

76.7 

170 

11.5 

64.5 

25.4 

54.5 

130 

31.5 

44.5 

17.5 

77.1 

171 

12 

64 

25.2 

55.4 

132 

32 

44 

17.3 

77.5 

171 

12.5 

63.5 

25.0 

56.3 

133 

32.5 

43.5 

17.1 

77.9 

172 

13 

63 

24.8 

57.2 

135 

33 

43 

16.9 

78.2 

173 

13.5 

62.5 

24.6 

58.0 

136 

33.5 

42.5 

16.7 

78.6 

173 

14 

62 

24.4 

58.7 

138 

34. 

42 

16.5 

79.0 

174 

14.5 

61.5 

24.2 

59.5 

139 

34.5 

41.5 

16.3 

79.3 

175 

15 

61 

24.0 

60.2 

140 

35 

41 

16.1 

79.7 

175 

15.5 

60.5 

23.8 

61.0 

142 

35.5 

40.5 

15.9 

80.0 

176 

16 

60 

23.6 

61.6 

143 

36 

40 

15.7 

80.4 

177 

16.5 

59.5 

23.4 

62.3 

144 

37 

39 

15.3 

81.0 

178 

17 

59 

23.2 

63.0 

145 

38 

38 

15.0 

81.7 

179 

17.5 

58.5 

23.0 

63.6 

146 

39 

37 

14.6 

82.4 

180 

18 

58 

22.8 

64.2 

148 

40 

36 

14.2 

83.0 

181 

18.5 

57.5 

22.6 

64.8 

149 

41 

35 

13.8 

83.6 

182 

19 

57 

22.4 

65.4 

150 

42 

34 

13.4 

84.2 

184 

19.5 

56.5 

22.2 

66.0 

151 

43 

33 

13.0 

84.8- 

185 

20 

56  ' 

22.0 

66.5 

152 

44 

32 

12.6 

85.4 

186 

20.5 

55.5 

21.8 

67.1 

153 

45 

31 

12.2 

86.0 

187 

21 

55 

21.6 

67.6 

154 

46 

30 

11.8 

86.5 

188 

21.5 

54.5 

21.5 

68.1 

155 

47 

29 

11.4 

87.1 

189 

22 

54 

21.3 

68.7 

156 

48 

28 

11.0 

87.7 

190 

22.5 

53.5 

21.1 

69.2 

157 

49 

27 

10.6 

88.2 

191 

23 

53 

20.9 

69.7 

157 

50 

26 

10.2 

88.7 

192 

APPENDIX  I. 


317 


5a.  TABLE  or  TEMPERATURES  CORRESPONDING  TO  THE  TENSIONS  OF  SATU- 
RATED STEAM. — Continued. 


iff 

«6* 

Vacuum 

Temperature. 

Absolute 
pressure 
in  cm. 

Vacuum. 

Temperature. 

cm. 

inches. 

C.° 

F.° 

cm. 

inches. 

C.° 

F.° 

51 

25 

9.84 

89.2 

193 

64 

12 

4.72 

95.3 

203 

52 

24 

9.45 

89.7 

193 

65 

11 

4.33 

95.7 

204 

53 

23 

9.06 

90.2 

194 

66 

10 

3.94 

96.1 

205 

54 

22 

8.66 

90.7 

195 

67 

9 

3.54 

96.5 

206 

55 

21 

8.27 

91.2 

196 

68 

8 

3.15 

96.9 

206 

56 

20 

7.87 

91.7 

197 

69 

7 

2.76 

97.3 

207 

57 

19 

7.48 

92.2 

198 

70 

6 

2.36 

97.7 

208 

58 

18 

7.09 

92.6 

199 

71 

5 

1.97 

98.1 

209 

59 

17 

6.70 

93.1 

200 

72 

4 

1.57 

98.5 

209 

60 

16 

6.30 

93.5 

200 

73 

3 

1.18 

98.9 

210 

61 

15 

5.91 

94.0 

201 

74 

2 

.79 

99.3 

211 

62 

14 

5.51 

94.4 

202 

75 

1 

.39 

99.6 

211 

63 

13 

5.12 

94.8 

203 

76 

0 

.0 

100.0 

212 

318  APPENDIX   I. 

5. — (6)  FROM  0  TO  1  ATMOSPHERE  EXCESS  PRESSURE. 


If! 

0)  C  =- 

Pressure  over 
one  atmosphere 

Temperature. 

;l<f 

®  c  ^ 

Pressure  over 
one  atmosphere 

Temperature. 

III 

in  cm. 

in  Ibs. 

I      S.S   £> 

115 

in  cm. 

in  Ibs. 

J5o 

of  mer- 

per 

C° 

Fo 

^§o 

of  mer- 

per 

C° 

Fo 

^ 

cury. 

sq.  in. 

<u 

cury. 

sq.  in. 

76 

0 

0 

100.0 

212.0 

115 

39 

7.53 

112.0 

233.5 

77 

1 

0.19 

100.4 

212.7 

116 

40 

7.72 

112.2 

234.0 

78 

2 

0.39 

100.7 

213.3 

117 

41 

7.91 

112.4 

234.5 

79 

3 

0.58 

101.1 

214.0 

118 

42 

8.11 

112.7 

235.0 

80 

4 

0.77 

101.4 

214.6 

119 

43 

8.30 

112.9 

235.5 

81 

5 

0.96 

101.8 

215.2 

120 

44 

8.49 

113.2 

235.9 

82 

6 

1.15 

102.1 

215.8 

121 

45 

8.68 

113.5 

236.3 

83 

7 

1.35 

102.5 

216.4 

122 

46 

8.87 

113.7 

236.7 

84 

8 

1.54 

102.8 

217.0 

123 

47 

9.07 

113.9 

237.1 

85 

9 

1.74 

103.2 

217.6 

124 

48 

9.26 

114.2 

237.6 

86 

10 

1.93 

103.5 

218.2 

125 

49 

9.46 

114.4 

238.0 

87 

11 

2.12 

103.8 

218.8 

126 

50 

9.65 

114.7 

238.4 

88 

12 

2.32 

104.1 

219.4 

127 

51 

9.84 

114.9 

238.8 

89 

13 

2.51 

104.4 

220.0 

128 

52 

10.04 

115.2 

239.3 

90 

14 

2.70 

104.7 

220.6 

129 

53 

10.23 

115.4 

239.8 

91 

15 

2.89 

105.1 

221.2 

130 

54 

10.42 

115.7 

240.2 

92 

16 

3.08 

105.4 

221.7 

131 

55 

H).61 

115.9 

240.6 

93 

17 

3.28 

105.7 

222.3 

132 

56 

10.80 

116.1 

241.0 

94 

18 

3.47 

106.0 

222.8 

133 

57 

11.00 

116.3 

241.4 

95 

19 

3.67 

106.3 

223.3 

134 

58 

11.19 

116.6 

241.8 

96 

20 

3.86 

106.6 

223.9 

135 

59 

11.39 

116.8 

242.2 

97 

21 

4.05 

106.9 

224  .4 

136 

60 

11.58 

117.1 

242.7 

98 

22 

4.25 

107.2 

225.0 

137 

61 

11.77 

117.3 

243.1 

99 

23 

4.44 

107.5 

225.5 

138 

62 

11.97 

117.5 

243.5 

100 

24 

4.63 

107.8 

226.0 

139 

63 

12.16 

117.8 

244.0 

101 

25 

4.82 

108.1 

226.6 

140 

64 

12.35 

118.0 

244  .4 

102 

26 

5.01 

108.4 

227.1 

141 

65 

12.54 

118.3 

244.9 

103 

27 

5.21 

108.7 

227.7 

142 

66 

12.73 

118.5 

245.3 

104 

28 

5.40 

109.0 

228.2 

143 

67 

12.93 

118.7 

245.7 

105 

29 

5.59 

109.3 

228.7 

144 

.    68 

13.12 

118.9 

246.1 

106 

30 

5.79 

109.6 

229.2 

145 

69 

13.32 

119.1 

246.5 

107 

31 

5.98 

109.8 

229.7 

146 

70 

13.51 

119.4 

246.9 

108 

32 

6.18 

110.1 

230.2 

147 

71 

13.70 

119.6 

247.3 

109 

33 

6.37 

110.3 

230.6 

148 

72 

13.90 

119.8 

247.7 

110 

34 

6.56 

110.6 

231.1 

149 

73 

14.09 

120.0 

248.0 

111 

35 

6.75 

110.9 

231.6 

150 

74 

14.28 

120.2 

248.4 

112 

36 

6.94 

111.1 

232.0 

151 

75 

14.47 

120.4 

248.7 

113 

37 

7.14 

111.4 

232.5 

152 

76 

14.67 

120.6 

249.1 

114 

38 

7.33 

111.7 

233.0 

APPENDIX  I. 


319 


5. — (c)  Relation  between  the  different  units  for  measuring  vacuo 


Atmos- 
pheres at 
absolute 
pressure. 

Atmos- 
pheres of 
vacuo 

Kilo*  of 
absolute 
pressure. 

Kilos  at 
vacuo. 

Milli- 
metres of 
mercury, 
absolute 
pressure. 

Milli- 
metres of 
mercury 
vacuo. 

Inches  of 
mercury, 
absolute 
pressure. 

Inches  of 
mercury, 
vacuo. 

0.1 

0.9 

0.103 

0.930 

76 

684 

3 

27 

0.2 

0.8 

0.207 

0.826 

152 

608 

6 

24 

0.3 

0.7 

0.310 

0  723 

228 

532 

9 

21 

0.4 

0.6 

0.413 

0.620 

304 

456 

12 

18 

05 

0.5 

0.517 

0.516 

380 

380 

15 

15 

0.6 

0.4 

0.620 

0.413 

456 

304 

18 

12 

0.7 

0.3 

0.723 

0.310 

532 

228 

21 

9 

0.8 

0.2 

0.827 

0.206 

608 

152 

24 

6 

0.9 

0.1 

0.930 

0.103 

684 

76 

27 

3 

1.0 

00 

1.033 

0.000 

760 

000 

30 

0 

(d)  RELATION  BETWEEN  THE  DIFFERENT  UNITS  FOR  MEASURING  PRESSURE. 


Atmos- 
pheres of 
absolute 
pressure. 

Atmos- 
pheres of 
pressure. 

Kilos 
per 
sq.  cm. 

Pound* 
>     per 
sq.  in.      i 

Atmos- 
pheres of 
absolute 
pressure. 

Atmos- 
pheres of 
pressure. 

Kilos 
per 
sq.  cm. 

Pounds 
per 
sq.  in. 

1 

0 

0 

o 

7 

6 

6.200 

88.0 

2 

1 

1.033 

14.7 

8 

7 

7.234 

102.7 

3 

2 

2.067 

29.  -5 

9 

8 

8.267 

117.4 

4 

3 

3.100 

44.0 

10 

9 

9.301 

132.1 

5 

4 

4.134 

5S.7 

11 

10 

10.334 

146.7 

6 

5 

5.167 

73.4 

- 

320 


APPENDIX  I. 


-II.   TABLE  FOR  THE' BOILER  HOUSE  (Fliegener's). 
0.1  to  10  Atmospheres. 


Pressure. 

Temperature. 

Kilos  per 
sq.  cm. 

Cen  timeters 
of  mercury. 

Pounds  per 
sq.  inch. 

Centigrade.. 

Fahrenht-it. 

0.1 

7.355 

1.42 

45.6    : 

114.1 

0.2 

14.71 

2.84 

59.8 

139.6 

0.3 

22.07 

4.26 

68.7 

155.7 

0.4 

29  .  42 

5.68 

75.5 

167.9 

0.5 

36.78 

7.11 

80.9 

177.6 

0.6 

44.13 

8.51 

85.5 

185.9 

0.7 

51.49 

9.95 

89.5 

193.1 

0.8 

58.84 

11.36 

93.0 

199.4 

0.9 

66.20 

12.79 

96.2 

205.2 

1.0 

73.55 

14.21 

99.1 

210.4 

1.5 

110.3 

21.32 

110.8 

231.4 

2.0 

147.1 

28.42 

119.6 

247.3 

2.5 

183.9 

35.53 

126.7 

260.1 

3.0 

220.7 

42.63 

132.8 

271.0 

3.5 

257.4 

49.74 

138.1 

280.6 

4.0 

294.2 

56.84 

142.8 

289.0 

4.5 

331.0 

63.95 

147.1 

296.8 

5.0 

367.8 

71.05 

151.0 

303.8 

5.5 

404.5 

78.16 

154.6 

310.3 

6.0 

441.3 

85.26 

157.9 

316.2 

6.5 

478.1 

92.27 

161.1 

322.0 

7.0 

514.9 

99.47 

164.0 

327.2 

7.5 

551.6 

106.58 

166.8 

332.2 

8.0 

488.4 

113.7 

169.5 

337.1 

8.5 

625.2 

120.8 

172.0 

341.6 

9.0 

662.0 

127.9 

174.4 

345.9 

9.5 

698.7 

135.0 

176.7 

350.1 

10.0 

735.5 

142.1 

178.9 

354.0 

APPENDIX    I. 


321 


6.  TABLE  SHOWING  THE  SPECIFIC  HEAT  OF  STEAM  AT  DIFFERENT 

PRESSURES  AND  TEMPERATURES. 
(Zeitschrift  Deutscher  Ing.  1907,  Nr.  3  u.  4.) 
Values  of  Cp. 


Pressure,  Atm.  kg.  per  1  cm* 

1 

2 

4 

6 

8 

10 

12 

20 

Saturation  temperature.     C°. 

99 

120 

143 

158 

169 

179 

187 

211 

At  the  saturation  temp'ture 
At  100             

Specific  Heats. 

0.463 
0.463 
0.462 
0.462 
0.466 
0.474 
0.490 
0.511 

0.480 

0.476 
0.472 
0.473 
0.478 
0.492 
0.512 

0.513 

0.510 
0.492 
0.484 
0.485 
0.497 
0.515 

0.548 

0.513 
0.491 
0.490 
0.500 
0.517 

0.583 

0.538 
0.499 
0.493 
0.503 
0.519 

0.621 

0.572 
0.506 
0.497 
0.506 
0.521 

0.660 

0.613 
0.514 
0.500 
0.508 
0.522 

0.865 

0.559 
0.508 
0.513 
0.527 

At  150  

At  200 

At  250                   

At  300               

At  350             

At  400 

7.  TABLE  SHOWING  THE  INCREASE  IN  BOILING-POINT  OF  PURE  AND  IMPURE 

SUGAR  SOLUTIONS. 
Claassen  (Vereinszeitschrift  1904,  S.  1161.) 


Increase  in  boiling  point  for  a  solution  of  purity. 


ill 
£-g 

100 

93 

83 

73 

62 

C° 

F° 

C° 

F° 

C° 

F° 

C° 

F° 

C° 

F° 

5 

0.05 

0.09 

0.05 

0.09 

0.05 

0.09 

0.05 

0.09 

0.05 

0.09 

10 

0.1 

0.18 

0.1 

0.18 

0.1 

0.18 

0.15 

0.27 

0.2 

0.36 

15 

0.2 

0.36 

0.2 

0.36 

0.25 

0.45 

0.25 

0.45 

0.35 

0.63 

20 

0.3 

0.54 

0.3 

0.54 

0.35 

0.63 

0.40 

0.72 

0.5 

0.90 

25 

0.45 

0.81 

0.45 

0.81 

0.5 

0.9 

0.6 

1.1 

0.75 

1.4 

30 

0.6 

1.1 

0.65 

1.2 

0.7 

1.3 

0.85 

1.6 

1.1 

2.0 

35 

0.8 

1.4 

0.85 

1.5 

1.0 

1.8 

1.2 

2.2 

1.5 

2.7 

40 

1.05 

1.9 

1.15 

2.0 

1.35 

2.4 

1.6 

2.9 

1.95 

3.5 

45 

1.4 

2.5 

1.55 

2.8 

1.75 

3.2 

2.1 

3.8 

2.5 

4.5 

50 

1.8 

3.2 

2.0 

3.6 

2.25 

4.0 

2.7- 

4.9 

3,15 

5.7 

55 

2.3 

4.1 

2.6 

4.7 

3.0 

5.4 

3.5 

6.3 

4.0 

7.2 

60 

3.0 

5.4 

3.3 

5.9 

3.8 

6.9 

4.5 

8.1 

5.0 

9.0 

65 

3.8 

6.9 

4.25 

7.7 

4.8 

8.7 

5.6 

10.1 

6.2 

11.2 

70 

5.1 

9.2 

5.4 

9.7 

6.2 

12.1 

7.0 

12.6 

8.0 

15.4 

75 

7.0 

12.6 

7.3 

13.1 

8.5 

16.3 

9.2 

16.6 

10.3 

18.5 

80 

9.4 

16.9 

10.0 

18.0 

11.4 

20.5 

12.2 

22.0 

13.6 

24.5 

85 

13.0 

23.4 

13.4 

24.1 

15.9 

28.6 

16.9 

30.4 

18.2 

32.8 

90 

19.6 

33.3 

(20.0) 

(36.0) 

(22.0) 

(39.6) 

24.7 

44.5 

26.9 

48.4 

92 

24.0 

43.2 

— 

— 



— 

— 

— 

— 

— 

94 

30.5 

54.9 

L   -- 

~ 

~ 

""** 

~ 

322 


APPENDIX  I. 


8.  TABLE  GIVING  THE  SPECIFIC  HEATS  OF  SUGAR  SOLUTIONS. 
(Cf.  Curin,  Oest.  Zeitschrift,  1894,  p.  988.) 


Specific  heat  according  to 

Specific  heat  according  to 

Degree 

Degree 

Rriv 

Kopp. 

Marignac. 

Kopp. 

Marignac. 

1 

0.993 

0.994 

60 

0.605 

0.652 

10 

0.934 

0.942 

70 

0.539 

0.594 

20 

0.868 

0.884 

80 

0.474 

0.536 

30 

0.803 

0.826 

90 

0.408 

0.478 

40 

0.737 

0.768 

99 

0.349 

0.426 

50 

0.671 

0.710 

9.    TABLE    SHOWING   SUGAR-LOSSES   IN    THE   EVAPORATION   OF   ALKALINE 

JUICES. 

(Cf.  Herzfeld,  Deutsche  Vereinszeitschrift,  1893,  p.  754.) 
Sugar-losses  for  100  parts  of  sugar  in  one  hour. 


Sugar-content  of  the  juice. 

Boiling 

•temperature 

in  0°  C. 

10% 

20% 

30% 

40% 

50% 

80 

0.0444 

0.0301 

0.0157 

0.0179 

0.0200 

85 

0.0615 

0.0421 

0.0223 

0.0262 

0.0296 

90 

0.0790 

0.0541 

0.0290 

0.0344 

0.0392 

95 

0.0965 

0.0661 

0.0357 

0.0427 

0.0488 

100 

0.1140 

0.0781 

0.0423 

0.0508 

0.0584 

105 

0.1385 

0.0937 

0.0490 

0.0588 

0.0680 

110 

0.1630 

0.1093 

0.0557 

0.0667 

0.0776 

115 

0.1749 

0.1187 

0.0623 

0.0748 

0.0862 

120 

0.2823 

0.2341 

0.1857 

0.2269 

0.2678 

125 

0.5330 

0.5082 

0.4833 

0.5939 

0.7044 

130 

2.0553 

1.4610 

0.8667 

1.0235 

1  .  1800 

135 

3.5776 









140 

5.1000 

— 

— 

— 

— 

APPENDIX   I. 


323 


10.  TABLES  SHOWING  INFLUENCE  OF  PURITY  ON  YIELD. 

(Claassen,  D.  Zuckerind.     1894,  p.  956.) 

I.     Ox  YIKLD  OF  RAW-SUGAR. 


(o)  Influence  of  purity  of  massecuite  when 
purity  of  centrifugalled  sirup  is  72. 

(6)  Influence  of  purity  of  centrifugalled 
sirup  when  purity  of  massecuite  is  91. 

Massecuite, 

Yield  of 

Increase  of 

Yield  of 

Increase  of 

Total 
solids. 

Purity. 

(92°)  as  per 
cent  of 
massecuite. 

yield  per 
1  per  cent 
increase  in 
purity. 

Purity  of 
sirup. 

(92°)  as  per 
cent  of 
massecuite. 

1  per  cent 
increase  in 
purity. 

94 

88 

59.0 

— 

75 

66.7 

— 

94 

89 

62.7 

3.7 

74 

67.9 

1.2 

94 

90 

66.4 

3.7 

73 

69.1 

1.2 

94 

91 

70.1 

3.7 

72 

70.1 

1.0 

94 

92 

73.8 

3.7 

71 

71.0 

0.9 

94 

93 

77.5 

3.7 

70 

71.9 

0.9 

94 

94 

81.2 

3.7 

69 

72.7 

0.8 

94 

95 

84.9 

3.7 

68 

73.5 

0.8 







__ 

67 

74.2 

0.7 

•  — 

— 

— 

— 

66 

74.9 

0.7 

II.    ON  YIELD  OF  MOLASSES. 
PERCENTAGE  YIELD  ON  WEIGHT  OF  BEETS  OF  MOLASSES  CONTAINING  20% 

WATER. 
From  16%  a  Yield  of  First  Massecuite  and  a  True  Purity  of  the  Molasses  of  62. 


Average  polarization  of  the  sugar. 

of  the 
massecuite  or 

94 

95 

96 

97 

100 

thick   juice. 

Molasses  in  per  cent  of  the  beets. 

90 

3.3 

3.6 

4.0 

4.3 

4.9 

91 

2.7 

3.1 

3.4 

3.8 

4.4 

92 

2.1 

2.6 

2.9 

3.3 

4.0 

93 

1.6 

2.0 

2.4 

2.8 

3.5 

94 

1.1 

1.5 

1.9 

2.4 

3.0 

95 

0.6 

0.9 

1.4 

1.9 

2.5 

96 

0.0 

0.4 

0.8 

1.5 

2.0 

324 


APPENDIX    1. 


VARIOUS  DATA. 

One  cubic  meter  weighs: 

Washed  beets 550  to    600  kilos 

Fresh  residuum,  cosettes 600 

Soured  residuum,  cosettes 800 

Furnace  coke 420     u 

Gas  coke , .  350     " 

Limestone 1600     ' ' 

Lime 775  to    950     " 

Slaked-lime  paste 1200 

Raw  sugar,  firsts,  loosely  piled  up 875 

"        "       seconds,  loosely  piled  up 780 

Hot  massecuite 1450  to  1470     ' ' 

SPECIFIC  WEIGHTS. 

Sugar 1.61 

Limestone 2 . 36  to  2 . 74 

Lime 2.3    to  4. 2 

WEIGHT  OF  GASES  AT  0°  AND  760  MM.  ATMOSPHERIC  PRESSURE. 

1  litre  of  air 1 . 293  grams 

1           of  oxygen 1 . 430  ' ' 

1           of  nitrogen 1 . 256  " 

of  carbonic  acid 1 . 977 

of  sulphurous  acid 2 . 909 

carbon  monoxide ' .  1 . 250  ' ' 

steam  at  100°  C 0.506  " 

hydrogen 0.089  " 

illuminating-gas 0. 517  " 

SPECIFIC  HEAT  OF  GASES  AT  CONSTANT  PRESSURE. 

Air .'." 0.2375 

-  Oxygen 0.2175 

Nitrogen. . . . ; . . . 0.2438 

Carbon  dioxide 0 . 2396 

Carbon  monoxide 0 . 2450 

Hydrogen : 3.4090 

Steam  (old  value) 0 . 4750 

(For  new  value  see  Table  VI.) 


APPENDIX  I. 


325 


COEFFICIENT  OF  HEAT  TRANSMISSION,  DATA  OBTAINED  IN  PRACTICE 
(ACCORDING  TO  JELINEK). 

1st  compartment  37  calories 


Triple  effect  \  2d 
I  3d 
(1st.  compar 
3d 
14th 

25 
14 
ment  28  calories 
26 
20 
5  to  6  calories 

Vacuum-pan  for  after-products  6  to  7  calories. 

(Until  grain  formation,  18  calories 
During  graining,  10  calories 
During  thickening,  3.7  calories 
According  to  Claassen: 

1st  compart  ment,  fall  of  5°.5  temperature,  juice  at  10°  Brix,  40 

to  50  calorie.s 

2d  "  "    "  7°.5          "  juice  at  20°  to  25° 

Brix,  30  to  35  calories 

3d  "    "  24°  temperature,  juice  at  55°  to  62° 

Brix,  15  to  20  calories 


Triple  effect 


EXPERIMENTS  CONDUCTED  ON  A  SMALL  SCALE  AT  THE  ATMOSPHERIC  PRESSURE 
(ACCORDING  TO  SULZER). 


Kind  of  tube. 

Thick- 
ness, 

mm. 

Coefficient  of  heat  transmission  for 
the  steam  used  at  the  tempera- 
ture of 

110 
°C. 

117 
°C. 

125 
°C. 

131.3 
°C. 

136.5 
°C. 

141.6 
°C. 

1.  Drawn-copper  tube  .                     ... 

2.5 
2.1 
2.1 
4.5 
10 
13 
1.85 
15.25 
13.5 

19.0 
17.7 
26.2 

47.3 
33.3 
38.0 
40.5 
25.8 
23.2 
26.2 
20.5 
24.8 

57.2 
35.3 
36.7 
42.8 
32.2 
24.7 
31.3 
24.5 
28.0 

63.3 
35.8 
39.2 
44.8 
31.5 
26.2 
33.0 
25.0 
28.7 

62.3 
37.7 
39.2 
45.5 
31..3 
25.5 
38.3 
26.0 
30.0 

54.2 
35.3 
37.8 
43  3 
32.  a 
24.7 

25.7 
29.7 

2.  Wt.-iron  tube,  riveted  and  enameled 
3.  Wt.-iron  tube,  riveted  but  not  enam. 
4.   Welded  wrought  -iron  boiler  tube  .  .  . 
5.  Rough  cast-iron  tube  

6.  Welded  wrought  -iron  tube 

7.  Riveted  steel  enameled  tube 

8.  Cast-iron  smoothly  turned  tube  
9.  Cast-iron  corrugated  tube.    . 

In  the  preheater  for  diffusion  juices  with  moderate  circulation,  2  to  3  calories. 

rapid  circulation,  6  to  10  calories. 

DECOMPOSITION  OF  SUGAR  IN  ALKALINE  SOLUTIONS. 

1  cu.  cm.  of  a  caustic  potash  1/10  normal  (containing  0.0047  grams  K2O  = 
0.0028  gram  CaO)  is  neutralized  by  0.012  gram  of  inverted  sugar  or 
0.0114  gram  of  saccharose.  ^  ' 


APPENDIX  II  * 


CALCULATIONS  FOR  AN  EVAPORATING  PLANT  AND  FOR 
THE  STEAM  CONSUMPTION  IN  WORKING  UP  100  LBS. 
OF  BEETS. 

THE  following  calculations  do  not  claim  to  be  precise,  but  only 
show  in  a  simple  way  how  practical  data  can  be  obtained: 

Given:  The  evaporating  plant  consists  of  a  quadruple  effect 
and  juice-cooker.  Steam  for  heating  and  boiling  is  taken  as 
follows : 

For  Diffusion:  from  First  effect. 

"    First  juice-heater:  "     Fourth  effect. 

11    Second  juice-heater:  tl     Second  effect. 

".    Garbonatation  juice,  thin  juice  and  thickened  juice: 

from  First  effect. 

11    Pans:    half  is  taken  from  the  first  effect  and  half  from  the 
juice-cooker. 

From  100  Ibs.  of  beets  are  obtained  115  Ibs.  of  diffusion  juice 
and  125  Ibs.  of  carbonatation  and  thin  juices.  The  thin  juice  is 
concentrated  from  12°  to  60°  Brix.  The  amount  of  thickened 
juice  will  be  25  Ibs.,  and  the  amount  of  massecuites  15  Ibs.  Hence, 
from  the  thin  juice  100  Ibs.  of  water  will  have  to  be  evaporated; 
from  the  thick  juice,  10  Ibs. 

The  specific  heat  of  the  beets  and  thin  juices  is  0.9,  and  of  the 
thick  juice,  0.6. 

*  The  data  in  the  two  appendices  following  have  been  expressed  in  the 
U.  S.  units  of  measurement.  As  Dr.  Claassen  has  given  most  of  the 
data  in  parts  per  100,  comparatively  few  of  the  figures  are  changed,  except 
those  expressing  temperature,  heat-units,  transference  coefficients,  and 
heating-surfaces.  As  in  the  original  calculation,  round  numbers  are  given. 
— TRANSLATORS. 

326 


APPKXDIX    II.  327 

A.    For    the    heating   and    boiling   calculations,    the    following 
amounts  of  steam  are  used  : 

1.  For  the  Diffusion:    The  amount  of  heat  necessary  for  juice 

heating  is  the  difference  between  that  in  the  raw  juice, 
including  that  in  'the  spent  chips  and  waste  waters,  and 
the  amount  introduced  in  the  beets  and  water,  including 
cooling  losses. 
There  are  90  Ibs.  of  spent  chips  and  110  Ibs.  of  waste  water. 

The  temperature  of  the  beets  is  taken  at  50°  F.,  that  of  the 

pressure-water  being  50°  F.,  and  of  the  -raw  juice  95°  F.,  and  of 

the  spent  chips  and  waste  waters  68°  F. 

There  is  added:    (a)  100X0.9X18  +  215X18  B.T.U.,  and  car- 

ried away  (6)  (110  +  90)36+115X0.9X63  B.T.U. 

C9QQ 

Heat  consumption  (b-a):  8230  B.T.U.  *-r=jr  Ibs.  of  steam, 

*7  /  \J 

D  =8.5  Ibs. 

2.  For  heating  the  raw  juice:   In  the  first  preheater,  from  95°  to 

122°  F. 


115X27X0.9  B.T.U.     or       —    Ibs.  of  steam,  RJl  =2.9  Ibs. 

J  i\j 

In  the  second  preheater,  from  122°  to  185°  F.: 
115X63X0.9  B.T.U.  Ibs.  steam,  RJ2=6.7  Ibs. 


3.  For  heating  during  carbonatation: 

Cooling  during  carbonatation  and  filtration  ....  13° 

'  '      second  carbonatation  .........  18° 

Heating  from  185°  to  212°  F  .................  27° 

58° 

6525 
125X58X0.9  B.T.U.     or    -—  Ibs.  steam,    C=6.71bs. 

*s  I  v/ 

4.  For  reheating  the  thin  juice  and  boiling,  corresponding  to  36°  F.  : 

4050 
125X36X0.9  B.T.U.     or    -—  Ibs.  steam,        TJ  =4.1  Ibs. 


328  APPENDIX  II. 

5.  For  heating  the  concentrated  juice  from  158°  to  212°  F.: 

810 
25X54X0.6  B.T.U.     or    --  Ibs.  steam,  TV  =0.8  Ibs. 

6.  For  boiling  the  concentrated  juice  in  the  pans:    By  which 

10  Ibs.  of  water  is  evaporated: 

—  Ibs.  of  steam  =  10. 5  Ibs. 
0.95 

For  heating:  1.0 

11.5  Ibs.        5  =  11.5  Ibs. 


Total:          41. 2  Ibs. 
B.  Special  Consumption  of  Steam. 

1.  For  heating  thin  juice  from  212°  F.  to  the  boiling  tem- 

perature of  the  heater,  this  being  done  either  in 
the  heater  or  in  a  special  preheater  and  according 
to  the  temperature  required  taking  2-3  Ibs.  2  Ibs. 

2.  For  the  motive  power  of  engines:   For  every  100  Ibs. 

of  beets  worked  up  there  is  necessary  0.5-0.7 
horse-power  hours,  one  horse-power  hour  taking 
heat  corresponding  to  2.6  Ibs.  of  steam.  Heat 
used  in  round  numbers,  2  Ibs. 

3.  Cooling  losses: 

(a)  In  steam  lines 3  Ibs. 

(b)  In  apparatus,  etc 3  Ibs. 

6  Ibs.          6  Ibs. 

4.  Losses  from  leaks,  evaporation,  etc.,          (2-3  Ibs.)        3  Ibs. 

Total  special  steam-consumption,  13  Ibs. 

The  amount  of  engine  exhaust  in  most  factories  with  ordinary 
type  of  engines  is  usually  taken  as  averaging  30  Ibs.,  those  with 
modern  and  centralized  power  averaging  20  Ibs.  per  100  Ibs.  of 
beets. 


APPENDIX    II.  329 

The  following  diagram  shows  the  way  the  steam  is  taken  from 
the  evaporator  above  described: 

Exhaust  Steam,  =  30 
Juice-cooker,  I.  II.  III.  IV. 

£-5.5  D=  8.5  &72  =  6.7  #J=2.9 

C=  6.7 

*/=  4.1 

TJ=  0.8 

B=  6.0 

Total:        =26.1 

Designating  the  amount  of  steam  which  the  quadruple  will 
evaporate  from  100  Ibs.  of  beets  as  x,  this  will  be  found  in  round 
numbers : 

In  IV,  x 
III,  x 

II,    x+  6.7 
I,     x+  6.7+26.1 
JC,  x+  6.7     26.1+5.1-30 


Total,   5x  + 20. 1+52.2 +  5.5 -30  =  100 
Since  there  are  100  Ibs.  of  water  in  all  to  be  evaporated: 
z  =  10.4  tbs. 

Live  steam  only  passes  into  the  juice-cooker,  hence  it  is  here 
that  all  the  live  steam  for  evaporating  as  well  as  for  other  purposes 
enters  the  system. 

The  whole  of  the  steam  necessary  for  evaporating  is; 

Live 18.7  Ibs. 

Exhaust 30.0  " 

48.7 
Steam  specially  used  (£)  .  . .   13.0 

Total  steam  used  in  the  factory  for 

100  Ibs.  beets  .  .  61.7  Ibs. 


330  APPENDIX   II. 

If  in  the  boilers  1  Ib.  of  coal  evaporates  8  Ibs.  of  water,  the 
coal  consumption  will  be  7.7  Ibs.  of  water  per  100  Ibs.  of  beets. 
These  coal  and  steam  figures  apply  only  when  the  work  is  con- 
tinuous. Interruptions  and  Sunday  rest  periods  raise  them 
notably. 

In  the  single  effects  of  the  evaporating  plant  as  described 
above,  the  heat-units  transferred  or  amounts  of  water  evaporated 
per  100  Ibs.  of  beets  are  as  follows: 

Evaporated.  Heat  Transferred. 

In  juice-cooker 18.7  Ibs.  water  17,800  B.T.U. 

First  effect 43.2         '.*  41,200      " 

Second  effect 17.1         "  16,600      " 

Third  effect 10.5         "  10,400      " 

Fourth  effect 10.5         "  10,600      " 

100.0  Ibs.  water 

From  the  vapors  passing  out  of  the  last  effect,  2.9  Ibs.  will  be 
condensed  in  the  first  juice  heater,  only  7.0  Ibs.  going  to  the 
condenser.  From  the  pans,  11  Ibs.  of  vapors  pass  off,  so  that 
altogether  18  Ibs.  of  waste  vapors  are  condensed  per  100  Ibs.  of 
beets. 

The  amount  of  condensed  water  from  the  evaporators  is  dis- 
tributed as  follows: 

(a)  Water  at  a  temperature  above  212°  F. : 

From  the  exhaust-steam  pipe 5     Ibs. 

"  juice-heater 18.7   " 

"  first  effect 43.2    " 

"  second  effect ..  17.1    " 


84  Ibs. 

(b)  Water  at  about  212°  F.: 

From  the  pans 11.5  Ibs. 

"  third  effect 10.5    " 

"  thin-juice  heater 4.1    " 

"  thick-juice  heater 0.8    " 


26.9  Ibe. 


AITI;NDIX  n. 


331 


(c)  Water  below  212°  F.: 

From  the  fourth  effect 10.5  Ibs. 

diffusion  heaters 8.5   " 

"            diffusion  juice-heaters 9.6   " 

"            carbonatation  juice  heaters  ..  6.7   " 


35.3  Ibs. 
146.2  Ibs. 

Calculation  of  heating-surface  is  on  the  following  principle: 
Since  the  heat-transference  coefficient  is  the  heat  transferred 
from  one  square  foot  of  surface  per  degree  Fahrenheit  of  tempera- 
ture, in  order  to  determine  the  size  of  the  heating-surface  for  each 
vessel  it  is  necessary  to  divide  the  heat-units  which  are  transferred 
in  one  minute  in  each  vessel,  as  given  above,  by  the  product 
of  the  temperature  fall  and  the  heat-transference  coefficient.  For 
the  temperature  fall  in  the  preheaters,  take  the  difference  between 
the  temperature  of  the  steam  used  for  heating  and  the  mean 
temperature  of  the  juice  entering  and  leaving  the  apparatus. 
In  the  case  of  evaporating  and  boiling  apparatus,  the  difference 
of  temperature  between  the  steam  and  the  boiling  liquors  should 
be  taken. 

CALCULATION  OF  HEATING-SURFACE  FOR  100  LBS.  OF  BEETS  IN  1  MINUTE, 
CORRESPONDING  TO  A  DAILY  WORK  OF  ABOUT  50  TONS. 


Apparatus. 

Heat- 
units. 
B.T.U. 

Tempera- 
ture Fall 
inF°. 

Heat-trans. 
Coef. 
B.T.U. 

Heat- 
surf  are, 
Sq.Ft. 

J  uicG-cookcr 

17,800 

18 

8.3 

120 

First  effect 

41^200 

14 

7.5 

390 

Second  effect                

1^600 

16 

5.0 

210 

Third  effect  .  .         

10,400 

18 

3.3 

175 

Fourth  effect        

10,600 

31 

2.0 

170 

Raw  juice:  First  preheater  

2,800 

45 

0.8 

80 

Second  preheater  .  .  . 
Carbonatation:  Juice  heater  .... 
Thin-juice  heater 

6,500 
6,480 
4,050 

63 
36 

18 

0.8 
0.8 
1.7 

130 
225 
130 

Thick-juice  heater  

810 

54 

0.8 

20 

Vacuum-pans'  Fissts  

9,720 

54 

1.7 

105 

Sirup 

970 

54 

0  8 

20 

332  APPENDIX   II. 

Since  the  vacuum  pans  for  firsts  and  for  sirup  products  are 
not  working  continuously,  and  since  the  juices  do  not  all  boil 
down  equally  well,  it  is  advisable  to  provide  an  excess  of  from 
50  to  100  per  cent,  over  the  calculated  amount  of  heating  sur- 
face required.  Still  more  heating  surface  is  required  if  the 
evaporating  apparatus  is  not  thoroughly  cleaned  once  a  weak, 
or  if  there  is  much  scale  deposited  from  the  juice.  It  is  not 
necessary  to  provide  fqr  a  temporary  working-up  of  more  beets, 
for  instead  of  50  tons  per  day,  as  was  assumed,  100  Ibs.  per 
minute  is  actually  equivalent  to  62  tons  per  day.  This  com- 
putation, however,  is  for  apparatus  for  good  juice  circulation, 
and  does  not  hold  for  apparatus  of  antiquated  design. 

The  heating  surfaces  in  the  boilers  that  is  necessary  for 
delivering  62  Ibs.  of  steam  per  minute  (cf.  page  329)  can  be 
computed  according  to  the  following  principles:  To  utilize  the 
coal  efficiently,  1  square  foot  of  heating  surface  should  not  give, 
in  return  flue  boilers,  more  than  4  to  5  Ibs.  of  steam  per  hour, 
or  0.07  to  0.08  Ib.  per  minute;  in  multitubular  boilers  2.4  to 
3.2  Ibs.  per  hour  or  0.04  to  0.05  Ib.  per  minute.  Hence  for  the 
production  of  62  Ibs.  of  steam  per  minute  required  for  62  tons 
of  beets  daily  (here  it  is  not  necessary  to  make  a  deduction) 
there  are  needed  in 

Return  flue  boilers. 780  to     925  sq.  ft. 

Multitubular  boilers 1215  to  1460       " 

or  for  a  daily  working  of  50  U.  S.  tons, 

Return  flue  boilers 542  to    710  sq.  ft. 

Multitubular  boilers..  845  to  1015       " 


APPENDIX    II.  333 

HEAT  BALANCE  IN  THE  FACTORY, 
Calculated  for  100  pounds  beets  worked  up. 
(a)  Heat  loss  in  the  boiler-house : 

Goal  consumed,  7.7  Ibs,  12,240  B.T.U 94,250  B.T.U. 

Utilized:  61.7  Ibs.  of  steam  which,  when 
the  feed  water  is  at  203°  F.,  represents 

1000  B.T.U.  per  Ib 61,700      "    =  66% 

Lost 32,550      "     =  34% 

(6)  Heat  losses  in  the  sugar-house :  100% 

(The  per  cents,  are  on  the  heat-units  utilized  in  the  steam 
consumed,  taken  as  61,700  B.T.U.) 

1.  From  the  boiler-house  to  the  place  where 

utilized 5,040  B.T.U.  =  8.1% 

2.  In  the  condenser  waters.     In  condensa- 
tion, the  calculated  amount  of  steam 
used  is  18.6  Ibs.  which  is  increased  by 
various  irregularities  and  by  losses  in  re- 
moving ammonia  gases,  etc.,  to  about 

20  Ibs.  =20X1134  B.T.U 22,680      "      =36.5% 

3.  In  the  dumpings  from  the  diffusion,  200 

Ibs.  =200X18  B.T.U 3,600      "      =  5.8% 

4.  In   the  press-scums,  10  Ibs.  =10X108 

B.T.U 1,080      "      =  1.7% 

5.  In  the  water  condensed  from  the  evapo- 
rator vapors  and  not  utilized  for  boiler 
feed  and  sweetening  off,  about  65  Ibs.  = 

65X144  B.T.U 9,180     "      =14.7% 

(If  this  water  is  utilized  in  diffusion 
this  loss  belongs  to  the  diffusion 
dumpings.) 

6.  In  the  massecuites,  first  and  second, 
total  20  Ibs.  (specific  heat  0.5),  cooled 

126°  F 1,260  B.T.U.  =  2.0% 

Total  known  losses 42,840  B.T.U.  =68.8% 

Undetermined  losses 18,860      "      =31.2% 


APPENDIX   III. 


COMPARATIVE  REVIEW  OF  THE  STEAM  AND  COAL  CON- 
SUMPTION IN  DIFFERENT  SYSTEMS  OF  EVAPORATION 
AND  HEATING. 

IN  order  to  illustrate  more  fully  the  different  evaporator 
systems  and  to  show  the  way  the  vapors  and  steam  are  utilized 
in  heating  and  pan  boiling,  the  following  synopsis  has  been  made 
of  the  combinations  most  in  use.  Obviously  to  make  proper 
comparison,  all  conditions  except  the  arrangement  of  the  evapo- 
rating plant  and  the  method  of  steam  distribution  must  be  rigidly 
uniform,  and  these  data  are  so  set  forth  in  the  table.  In  such 
a  presentation  an  accurate  view  of  the  working  of  the  various 
evaporating  systems  can  be  obtained. 

In  the  table,  the  quantities  of  heat  which  are  taken  for  heating 
and  boiling  are  placed  under  the  appropriate  symbol  for  each 
body.  If  live  steam  is  taken  the  amount  is  given  in  a  special 
column.  The  amount  of  exhaust  is  taken  as  30  Ibs.,  if  no  figure 
is  given  over  those  of  the  first  effect. 

Steam  and  Fuel  Consumption. 

Given:  Raw  juice,  115  Ibs.     Thin  juice,  125  Ibs. 
Water  to  evaporate,  100  Ibs. 
Exhaust  steam,   30   Ibs.    (with   centralization   and   good 

engines,  20  Ibs.). 

Steam  for  heating:  Raw-j uice  heater,  I  (RJi)  =3  Ibs.  Raw- 
juice  heater,  II  (RJ2)  =7  Ibs.  Diffusion  (D)  =8  Ibs. 
Carbonatation  (C)  =7  Ibs.  Thin  juice  (tj)  =4  Ibs.  Thick 
juice  (7Y)=1  Ib. 

334 


APPENDIX  III. 


335 


Steam  for  boiling  the  thickened  juice,  11  Ibs.,  for  boiling 

sirup,  1  Ib.     Total  (B)  =12  Ibs. 
Special  uses  of  steam:  For  power  =2  Ibs.  for  heating  juice 

in  evaporators  =3  Ibs.     Cooling  losses  =6  Ibs.     Steam 

loss  =2  Ibs.     Total  =  13  Ibs. 
Water  evaporated  in  boilers:  8  Ibs.  per  1  Ib.  of  coal. 


Steam. 

Lbs. 

fYift.1      T  h<* 

Evap. 

Total. 

I       II      III 

72.3 

85.3 

10.7 

Z>  =  8     RJ2  =  7     C  =  7     0  =  4     TJ  =  l     B=12 

I          II               III 

RJ2  =  7 
C  =  7 
tf-4 
TJ=l 

63.3 

76.3 

9.5 

JH                I             II            III 
77-1 

55.6 

68.6 

8.5 

30  Ibs. 
JH,            JHU                I             II             IV 

7v  =  i         'r  =  7 

51.7 

64.8 

8.1 

20  Ibs. 
.///,            ./#„               I              II            III 

TJ=l             C  =  7 

47.8 

60.8 

7.6 

I         II         III         IV 
#./,  =  3 

64.0 

77.0 

9.6 

Z>  =  8     /2J2  =  7     C-7    0  =  4     T/=l     £=12 

I                II           III           IV 
D  =  8        RJ2-7                                   RJ^Z 
B  =  12          C  =  7 

59.3 

72.3 

9.0 

336 


APPENDIX   III. 


Evaporator  System. 

Steam.     Lbs. 

Coal.    Lbs. 

Evap. 

Total. 

£=12 

I               II           III         IV 

55.5 

68.5 

8.6 

I                II           III          IV 

T*\  O                  7~>    7      n                                            7~>    T     O 

7V=1 
£=12 

50.8 

63.8 

8.0 

JK 
£=12 

I              II            III          IV 

50.4 

63.4 

7.9 

TJ=1 

£K 
£2  =  4 

30  Ibs. 
I                II           III          IV 

tflf       RJcI77                 RJl  =  * 
TJ=l 

47.4 

60.4 

7.5 

J# 

20  Ibs. 
I               II           III         IV 

45-.  4 

58.4 

7.3 

tj=4           C  =  7 
TJ  =  l 

JH, 

20  Ibs. 
JHU          I           II         HI         IV 

42.3 

55.3 

7.3 

tj=4     C  =  7 
TJ=l 

JH, 

20  Ibs. 
JHn               I             II           HI          IV 

C=7 

42.3 

55.3 

6.9 

£,  =  8 

I 

II             III          IV           V 

45.4 

58.4 

7.3 

TJ  =  l 
£  =  12 

C  =  7 

INDEX. 


Acid,  caused  by  evaporation,  124 

for  purifying  sirups,  128,  174 

in  diffusion  juice,  47,  81 

in  thin  liquors,  159 
Acid,  hydrochloric  (muriatic) 

for  cleaning  filter-presses,  112 

for  removing  scale,  142 
After-products,  220 

alkalinity,  237,  240 

boiling  to  grain,  233 

•  covering,  238 
control  apparatus,  234 
'  crystallization  in  movement,  235 

in   crystallizers,  231 

froth  fermentation,  237 

temperature  for   boiling,  232,  235 

temperature  for  crystallizing,  230 
Albumen  in  juice,  47*  81 

filters,  83 
Alkalinity: 

boiler-feed,  258 

centrifugal  sirups,  240 

concentrated  juice  (sirup),  170 

diffusion  juice,  si 

filtered  juice,  115,  116 

first  carbonatation,  101-107 

first  green  sirup  carbonatation,  171 

increase  in  pan,  188 

in  defecation,  93,  101 

in  evaporation,  124 

over-saturated  juice,  105 

second  carbonatation,   123,  126 

sugar  crystals,  219 

thin  juice,  125 
Ammonia: 

from  juice,  138,  170 

in  evaporation,  139 

in  vacuum-pans,  175 

vents,  139,  176 
Antiseptic  agents,  130 

Beet  cells,  27 

changes  within,  28 

cell  tissue,  27 
Beets,  action  of  diffusion  upon,  37 

bins  for,  4 

cleaning,  6 

control  of  quality,  2 


Beets,  composition  of,  307 

cultivation,  1 

delivery  regulation,  4 

diseases,  11 

fibrous,  24,  26,  55 

frozen,  7,  15,  39,  42,  47,  52 

injured,  11,  15,  38,  47,  53 

quality  effect,  1,  281 

respiration,  7 

sampling,  6 

slicing,  20 

sprouts,  11 

storage,  7 

storage  temperature,  11 

sugar  loss  in  washing,  15 

temperature  borne  in  diffusion,  39 

tops,  6,  298,  299 

trimming,  6 

washing,  16 

weighing,  19,  282 

weight  gain,  9,  15 

weight  loss,  10 

weight  of,  324 

unsound,  39,  47,  53,  109 
j  Beet-slicers  (see  also  Knives),  20 
|  Beet  slices: 

amount  of  extraction,  41 

effect  on  action  of  presses,  62 

shape  and  size,  38 
Beet  slices,  exhausted: 

ash  of,  79 

changes  in  composition,  78 

drying,  74-80 

elevator,  60 

keeping  qualities,  80 

pressing,  61 

proportion  to  beets,  79 

removal  from  diffusers,  59 

sucrose  determination,   283 

transportation,  59 

treatment  with  molasses,   80 
Bins  for  beets,  4 
Boilers,  care  of,  259,  262,  295 

corrosion  of,  258 

feed- water  for,    162,   255 

injuries,  256,  258-260 

low-pressure,  258,  261 
Boiler-house,  254 

337 


338 


INDEX. 


Boiling    to    grain,    178,     181,    183. 

195 
super  -  saturation  -  coefficient,  179, 

182 
continuous  feed,  183 

Campaign,  opening  the,  3 
Carbonatation,    first:     97 

alkalinity,  78,  101,  102,  103,  107 

atomizing  juice,  98 

attention  of  workmen,  101 

automatic  juice  control,  106 

chemical   reactions,    103,    107 

continuous,  105 

depth  of  liquor,  100 

exit-pipes.  100 

frothing,  100,  109 

gas  distribution,  97 

general  method,  101 

insoluble  sucrates,  104 

juice  behavior,  102 

over-saturation,  105 

piping,  97 

slow,  108 

spoon  tests,  101,  102 

tanks,  97 

troubles,  108 

unfavorable  reaction,  104 
Carbonation,  second,  122 

alkalinity,  123,  126 

continuous,  preferable,  122 

effect  of  magnesia,  123,  127 

filtration  after,  127 

followed  by  third,  126 

reheating.  122 

Carbonatation  of  sirup  (thick  juice), 
171 

alkalinity,  172 

carbonic  or  sulphurous  acid,   172 

continuous,  172 

heating,  171 

lime,  172-4 

"  mittelsaft,"  173 

sucrates  present,  171 
Carbonic  acid   (carbon  dioxide),  97 

amount  in  kiln  gases,  269 

evolution  in  massecuite,  241 

in  diffusion,  55 

in  evaporation,  138 

in  sirup  Carbonatation,  171 

over-saturation,  105 

regulation  of  amount  for  juice,  101, 
116 

solvent  of  scums,  97 

under-saturation,  102 
Centralization,    of    condensers,    167 

of  engines,  275 

of  pumps,  167 


Centrifugals,  202 

continuous,  202 

feeding  of,  203 

purging  temperature  for,  205 

strainers  for,   202 

washing  sugars  in,  214 
Centrifugal  sirups,  220-253 

alkalinity,  240 

froth  fermentation,  241 

purifying  agents  for,  243 

returning  to  first  liquors,  243 
Chemical  control,  280 

duty  of  chemist,  281 

purpose,  281 

sugar  losses,  282 
Chip  (pulp)  eliminators,  61,  82 
Chip-presses,  61 
Circulator,  137 
Clarifying  agents,    128 
Cleanliness,  219,  293  A 

Cloths,  filter-press,  113 
Coal  consumption,  334 
Compressed  air: 

for  discharging  chips,  60 

for  removing  massecuite,  198 

for  stirring  massecuite,  230 

for  washing  sugars,  215 
Condensation  of  vapors,  165,  312 

amount  of  vapor,  164 

dry  and  wet  pumps,  165 
Condensers,  165 

amount  of  injection-water,  167 

central,  167 

efficiency,  166 

length  of  leg-pipe  for,  167 
Condensed  water: 

amount  recovered,  164 

for  boiler-feed,  162,  255,  258,  259 

for  washing  filter-presses,  119 

removal  from  evaporator,  134,  138. 
162 

removal  from  vacuum-pan,  177 

temperature,  57,  149,  255 
Cossettes  (see  beet  slices.} 
"Covering  process,"  238 
Crystal    foundation,    178,    182,    221, 

226,  231,  233 
Crystallizers,  185,  195,  198,  220 

methods  of  use,  199 

"Kochmaischen,"   200 
Cultivation  control,  1 

Defecation,  87 
alkalinity  in,  93 
continuous,  89 
dry,  88 

duration  of,  95 
lime  for,  00 


INDEX. 


339 


Defecation,  sucrates  in,  91 

temperature  during.  '.»4 
\\ash in u-scums  from,  90 

wet,  87 

Diatomaceous  earth,  use  of,  95,  172 
Diffusion,  28-63 

action  on  beet  chips,  28 

albumen  coagulation,   51 

carelessness,  56 

chemical  control,  57 

circulation,  32,  51,  57 

economizing  steam,  35 

effect  of  air,  34,  52 

evolution  of  gas,  54 

explosions.  .~>4 

hot  water  in,  35 

juice  determinations,  45 

micro-organisms,  47 

poor  pressure  in,  32,  51,  57 

starting,  57 

stopping  or  "sweetening  off,"  58 

temperature,  39,  51,  56 

test  of  best  method,  45 

warming  juice,  34 
Diffusion  cells,  29 

air-cocks,  34,  54 

air  in,  34,  52 

air  pump  for,  52 

automatic  juice  measurer,  44 

beams  or  gratings  in,  33 

"feeding  capacity/'  40 

form  and  capacity,  29 

form  of  upper  and  lower  parts.  31 

number,  29 

piping  for,  34 

relation  of  diameter  to  height,  30 

strainers,  32 
Diffusion  juice: 

amount,  132 

cause  of  color,  81 

composition  of,  81,  305 

expressed  juice,  standard  for,  45 

extraction,  43 

measurement.  44 

preliminary  purification,  83 

properties  S3 

purity,  44.  4."> 

purity  in  last  cell,  42 

temperature,  39 

tests.  44 

warming,  34 
Dryer< : 

for  exhausted  chips  Cslices),  74-78 

for  sugar,  see  Granulators. 

Electric  control  of  pumps,   101 
Klfdric   purification  of  juices,    130, 
251 


Elevators,  19 

Equipment  suggestions,  289-296 

effect  of  local  conditions,  289 

increasing  capacity,  291 

new  appliances,  292 

stoppages,  291 
Evaporation,  131 

concentration  required,  131 

effect  on  alkalinity,  124 

efficiency  of  steam,  132 

formula  for,  310,  311 

heat-transference  in,  133,  138,  145, 
155 

influence  of  acid,  159 

influence  of  viscosity   144 

present  methods  satisfactory,  163 

quantity  of  liquors,  131,  132 

temperature  fall,  148 

uncondensed  gases  in,  138 
Evaporators: 

accessories,  132 

capacity,  132,  155 

circulation,  137 

cleaning,  142 

control,  159 

efficiency,  132,  156,  160,  163 

entrainment  of  juice-spray,  147 

gas  in,  138 

heating  surfaces,  141,  149,  155 

heat-transference  coefficients,   155 

juice-catchers,  146,  147 

juice-feed,  161 

juice-level,  135,  159 

leaks,  145,  163 

multiple  effect,  148 

number  of  effects,  148 

scale,  125,  141,  142,  154 

single  effect,  135 

size  of  effect,  149 

steam-pressure,  154 

sugar  loss,  158 

temperature  drop,   134,   148,   154, 
160 

time  juice  remains,  158 

vacuum,  152,  159,  162 

valves,  158 

vapor  movement,  148 

vapors  for  heating  juice,  153 

Factory: 

care    of    machinery,    294 

cleanliness,  219,  293 

cost  of  operation,  1.  293 

data  of  working,  291 

"feeding  capacity,"  40 

journal,  294 

repairs,  294 
Fermentation,  froth  in  diffusers,  53 


340 


INDEX. 


Fermentation  in  massecuites,  241 
Filter-presses: 

cleaning,  112 

cloths,  113 

for  first  filtration,  110 

for  second  filtration  of  their  juices, 
127 

influence  of  magnesia,  123,  127 

pressure  for,  110 

size,  111 

slow  running,  115,  126 

types,  110 

washing,  116 
Filter-press   cake    (scums)    (sludge): 

composition,  297 

disposal,  298 

for  fertilizer,   121,  297 

formation,  114 

physical  condition,  297 

proportion  to  lime,  120 

soft,  115 

sugar  in,  116,  126,  283 

thickness,  112 
Froth,  in  diffusers,  53 

in  carbonatation,  109 
Formula? : 

calculation  of  amount  massecuite, 
310 

condensation,  312 

evaporation,  310,  311 

heat  transmission  through  a  metal 
wall,  312 

saturation  for  sirups,  311 

sugar  yield,  310 

Gas  in  diffusers,  54 
in  evaporators,  138 
in  vacuum-pan,  175 

.Gas  from  kiln,  269 

Gas-pumps,  269 

Gas-vents,  34,  54,  139 

Gas-washers,  268 

Gauges: 

for  boiling  control,  187 

for  evaporators,  132,  161 

for  gas-washers,  269 

for  scum-pumps,  110 

for  vacuum-pans,  176,  187,  227 

protecting  from  oil  in  boilers,  260 

Granulators,  217 

Grain  foundation  (see  crytsal  founda- 
tion) 

"Green  sirup,"  216 

Heat  balance,  333 

Heat  formula?,  311-325 

Heating  surface,  calculation  of,  331 


Heat  transference,  133,  138,  145,  150, 
155 

coefficient,  155,  331 

in  last  effect,  153 

Heat     transmission     through     films 
of  liquid,  133 

through  a  metal  wall,  133,  312,  325 
Hydraulic  carriers,  13 

choking,  14 

for  exhausted  chips,  59 

inclination,  14 

stone-eliminator,  15 

sugar  loss  from,  15 

water-supply,  14,  168 

Infusorial  earth,  use  of,  95,  172 

Juice  (see  "diffusion  juice") 
Juice-catchers,   146 
Juice-cooker,  152 
Juice-heaters,  34 

Knives,  beet: 
choice  of,  25 
counter,  20 
"dachrippen,"  25 
double,  25 
finger,  52 
fitting,  24 

for  fibrous  beets,  24 
holders,  23 
Konigsfelder,  25 
requirements,  23 
sharpening,  26 
size,  24 

Lime: 

action  on  raw  juice,  91 

amount  present  in  milk  of  lime,  314 

amount  used  in  defecation,  95 

"dead  burned,"  264 

decomposing  action  on  non-sugars, 
92 

in  diffusion  juice,  82 

in  molasses  purification,   249 

in  sirup,  172 

milk  of,  87,  314 

purifying  waste-water,  302 

quality,  88,  248 

slaking  heat,  89 

slaking   with    "sweet    water/'    88 

solubility  in  sugar  solutions,  314 

solubility  in  water,  314 

withdrawing  from  kiln,  266 
Lime-kilns,  263-270 

coke  for,  266 

size,  265 

temperature,  265 


IXDEX. 


341 


Limestone: 

chemistry  of   burning,   264 
choice,  263 
impurities,  2»il 

Massecuito: 

composition  of,  305 

cooling  of,  204 

crystallization,  200 

effect  of  purity  on  yield,  323 

finishing.  1st 

finishing  second,  in  pan,   196 

first,  202 

for  cold  purging,  197 

for  crystallizing,  184,  196,  189 

formulae  for  calculating  th  eamount, 
310 

influence  of  purity  on  yield,  323 

Kochmaischen,  200 

lumps  in,    192 

properly  boiled,  184 

stiff  second,  229 

stirring,   180,  230 

sugar  determination  of,  283 

temperature  of,  229 

thin  or  stiff,  198 
Mittelsaft,  173 
Molasses  composition  of,  224,  225,  305 

defined,  245 

effect  of  purity  on  yield,  323 

for  fodder,  252 

lowest  purity,  245 

osmosis  of,  247 

precipitation,  248 

purification  when  concentrated,  249 

purity,  233,  236 

transportation.  250 
"Monte  jus,"  110,  161 
Multiple-effect  evaporators  (see 

"evaporators.") 

Oil  (fats.) 

in  carbonatation,   100,   109 
in  evaporation,   163 
injuring  boilers,  256,  260 
removal  from  exhaust  steam,  260 

Piping: 

for  diffusion  cells,  34 

for  steam,  274.  296 

painting  of,  296 
Pressure  of  steam,  316 

units  for  measuring,  319 
Pulp  catchers.  61,  82 
Pure-juice-and-f odder,  process,  70 
Purifying  agents,  12s 

for*  centrifugal   sirups,    243 
Purity,  effect  on  yield,  323 


Raw  sugar,  207 
appearance.  209 
changes  in  storage,  210,  212 
color,  210 
form  of  crystal,  210 
packages,  212 
quality.  _ 
sifting,  211 
storage-room,  212 
transportation,  212 

Sampling,  280,  281,  294 

of  beets,  6 

of  condensed  vapors,  147 

of  hot  well-waters,  286 

of  press  residues,  286 

of  scums,   286 
Scalding  process,  70 
Scale  in  evaporators,  141 

composition  of,  141 

in  boilers,  259 

in  vacuum-pans,  192 

removal,  142 
Scum     treatment,     110     (see     also 

FHter-pressets] 
Sirup  ("thick  juice") 

alkalinity,  125,  170,  171 

ash  content,  171 

carbonatation,  171,  172 

color,  170,  174 

composition,  305 

concentration,  131 

entrainment,  146 

filtration,  172,  173 

hard  boiling,  171,  190-192 

heat-transference    coefficient,    155 

lime  in,   171,   190,   191 

liming,  172 

purity  effect   on  boiling.    1SG 

purity  effect  on  yield,  326 

supersaturation     coefficient,     181, 
182,  is;> 

temperature.    145,    Us.    171.    1>1 

viscosity,,  144,  146.  lv» 
Slicing  machines,  20 
Slicing  of  beets.  20 
Specific  heats,  321,  322.  324 
Specific  weights,  324 
Spoon  test,  101,  102 
Steam: 

amount  used  in  evaporation,  149- 
1 5x,  326-332 

coM.  278 

direct  injection  in  juice-heating,  :jt 

direct    injection    in    sugar-boiling, 
180,  193 

economizing  in  diffusion,   35 


342 


INDEX. 


Steam : 

heating  efficiency,  149 

in  multiple-effect,  329 

regulation  in  sugar-boiling,  178 

superheated,  273,  276 
Steam,  apparatus,  care  of,  295 
Steam,  exhaust: 

increasing  pressure,   154,   157 

in  juice-cooker,  154 

pressure,  145,  148,  157,  318 

specific  heat  of,  321 

temperature  of,  145,  316 

usually  not  sufficient,  166 

utilizing,  156 
Steam,  live: 

at  two  pressures,  261 

consumption  of,  156,  326-336 

controlled  by  juice-cooker,  153 

for  heating  juice,  34 

for  juice-cooker,  153 

used  in  starting,  158 
Steam  mantle,  Russian,  215 
Steaming  out  pans,   193,  194 
Stone  eliminators: 

for  hydraulic  carriers,  15 

for  scum-pumps,  110 
Stones,    removal    from    beet-slicers, 

22 

String  proof,  183 
Sucrates: 

in  carbonatation,  104 

in  filter-cake,  126 

precipitated  from  molasses,  249 

in  recovered  liquors,  250 
Sugar,  solubility  of,  315 

decomposition  of,  in  alkaline  solu- 
tion, 325 
Sugar-boiling,  175 

control,    186 

destruction  of  sugar,  188,  322 

entrainment,  189 

finishing  seconds,  220 

for  crystallizer,  185 

for  mixer,  direct,   185 

for  tanks,  184 

grain-forming  condition,  181 

"heavy,"  190 

learned  experimentally,  178 

string  proof,  183 
Sugar  crystals: 

by   washing   massecuite,    217 

by  washing  with  sirup  in  centrifu- 
gals, 215 

composition,  305 

granulated,  214,  217 

granulator  for,  217 

Pile"e  (loaf-sugar),  214,  217 

preparation,  214 


Sugar  losses: 

apparent,  284 

by  leakage  of  juice-heaters,  35 

in  beets,  10,  15 

in  evaporators,   147,   158 

in  pans,  188 

in  scums,  116,  119,  173 

known  (determinable),  283 

mechanical,  287 

summary,  286 

unknown    (undetermined),    284 
Sugar-refining  defined,  214 
Sulphurous  acid,  270 

burners  for,  271 

in  second  carbonatation,   123 

in  sirup  carbonatation,   171,   172, 
173,  174 

liquid,  270 
Super-saturation-coefficient  of  sugar 

solutions,  179,  185,  197,  198,  199, 

221,  226 
Tables: 

Heat-transmission  coefficients,  325 

Heat     transmission     experiments, 
325 

Lime,  solubility  of,  314 

Massecuite,  influence  of  purity,  323 

Molasses   composition,    224 
yield,  323 

Sirups,  saturation  coefficients,  223, 
311 

Steam  for  evaporating,  327 
in  multiple  effect,  329 
temperature  of,  316 

Sugar  solutions: 
boiling-point,  321 
effect  of  non-sugars  on  solubility, 

222 

effect  of  purity  on  yield,  323 
losses  in  evaporation,  322 
solubility  of  lime,  314 
solubility  in   water,   315 
specific  heats,  322 

Various  data,  324 
Temperature : 

effect  on  composition  of  molasses, 
225 

effect  on  sugar  decomposition,  158 

effect   on   viscosity   of   sirup,    226 

evaporation  vapors,  167 

for  filtering  scums,  119 

f or  massecuite  wash,  218 

for  reheating  for  second  carbona- 
tation, 122 

for  reheating  for  sirup  carbonata- 
tion, 171 

for  removing  albumen  from  juice, 
83 


INDEX. 


343 


Temperature: 

for  sugar  store-room,  213 

in  crystallizer  for    after-products, 

in  crystallizer  for  stiff  massecuites, 

199 
in  crystallizer  for  thin  massecuites, 

200 

in  juice-cooker.    1.11 
limit  of  heating  juice,  124 
of  adding  lime  in  dry  defecation, 

88 

of  condensed  water,  255 
of  cover  sirup,  240 
of  defecation,  87,  94 
of  diffusion  juice-heaters,  39 
of     diffusion     juice,     preliminary 

warming,  39,  70 
of  diffusion  water,  57 
of  drying  exhausted  beet  slices,  75, 

76 

of  exhaust  steam.  145 
of  hot-room,  22! » 
of  lime-kiln,  265 
of  massecuite  in  pan,  188 
of  sirup  in  last  effect,  148,  171 
of  steam,  316-3 IS 
of    steam    required    for    heating, 

151 

of  stored  beets,  11 
of   stored    granulated    sugar,    217 
of  vapors   from  evaporation,    167 
of  vapors  from  last  effect,  151 
of  waste  boiler-gases,  277 
practical    lower    limit    for    utiliz- 
ing heat,  277 
saturation   relation   of  centrifugal 

sirups.  221 

Temperature  drop  in  multiple  evap- 
orators, 131,  14S,  155,  160, 
325 


Ultramarine,  214 

Vacuum-pan,  175 

ammonia-vents,  139,  176 

continuous  feed,  183 

discharge-gate,  176 

equipment,  176 

heating  surfaces,  175,  176 

leaky  coils,  1S9 

size,  177,  1M 
Vapors,  evaporation : 

compressing,  156 

temperature  of.  167 

used  for  boiling,  154 

used   for   heating  cold  juice,    151 

velocity  in  evaporator,  147 
Various  data.  324 
Viscosity: 

effect  of  temperature,  226 

molasses,  225 

of  juice,  144 

Water: 

boiler-feed,  162,  255 

condensed,  149,  164 

for  transporting  beets,  14 

for  washing  filter-presses,  118 

injection,  166,  167 

pressure,  33,  46,  168 

supply,  150,  168 
Water,  waste,  300 

bacteria  of,  303 

purification.   300 

settling-tanks,  301 
Washing-machines : 

for  beets,  17 

for  filter-cloths,  113 
Weighing  of  beets,  19 

Yield,  calculation  of,  310 
YiekL  effect  of  purity  on,  323 


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